D&D 3E/3.5 Statistics for lethids (aboleth variants from Grim Tales)

[VelvetViolet]

I bought a used copy of Slavelords of Cydonia a while back. I thought the lethid and sli'ess were kind of cool and I was surprised to see that, despite the rules being open game content, they weren't reprinted elsewhere. (They're open game counterparts of illithids and yuan-ti, respectively.) I'll be copying the rules into this thread, in case anyone want to use them or convert them to PF2 or D&D5. (I apologize for any formatting oddities. The forum software doesn't seem to like copying rich text.)

To start with, here's the full section 15 for Grim Tales and Slavelords of Cydonia.

15. COPYRIGHT NOTICE
Open Game License v 1.0a Copyright 2000, Wizards of the Coast, Inc.
System Reference Document Copyright 2000, Wizards of the Coast, Inc.; Authors Jonathan Tweet, Monte Cook, Skip Williams, based on original material by E. Gary Gygax and Dave Arneson;
Modern System Reference Document Copyright 2002, Wizards of the Coast, Inc.; Authors Bill Slavicsek, Jeff Grubb, Rich Redman, Charles Ryan, based on material by Jonathan Tweet, Monte Cook, Skip Williams, Richard Baker, Peter Adkison, Bruce R. Cordell, John Tynes, Andy Collins, and JD Wiker.
System Reference Document Copyright 2000-2003, Wizards of the Coast, Inc.; Authors Jonathan Tweet, Monte Cook, Skip Williams, Rich baker, Andy Collins, David noonan, Rich Redman, Bruce R. Cordell, based on original material by E. Gary Gygax and Dave Arneson.
CORE Explanatory Notice, copyright 2003, Benjamin R. Durbin.
Spycraft Copyright 2002, Alderac Entertainment Group.
Swords of Our Fathers Copyright 2003, The Game Mechanics.
Mutants and Masterminds Copyright 2002, Green Ronin Publishing.
Unearthed Arcana Copyright 2004, Wizards of the Coast, Inc.; Andy Collins, Jesse Decker, David Noonan, Rich Redman.
Ultramodern Firearms d20, Copyright 2002, Charles McManus Ryan.
Modern Player’s Companion, Copyright 2003, The Game Mechanics, Inc.; Author: Stan!
Challenging Challenge Ratings: Immortals Handbook, Copyright 2003, Craig Cochrane.
Encountering Encounter Levels: Immortals Handbook, Copyright 2003, Craig Cochrane.
Design Parameters: Immortals Handbook, Copyright 2003, Craig Cochrane.
A Magical Medieval Society: Western Europe Copyright 2003, Expeditious Retreat Press; authors Suzi Yee and Joseph Browning.
Monster’s Handbook Copyright 2002, Fantasy Flight Publishing, Inc.
Monte Cook’s Arcana Unearthed, Copyright 2003, Monte J. Cook. All rights reserved.
Possessors: Children of the Outer Gods Copyright 2003, Philip Reed and Christopher Shy, www.philipjreed.com and www.studioronin.com.
Vilstrak from the Tome of Horrors, Copyright 2002, Necromancer Games., Inc.; Author Scott Greene, based on original material by Gary Gygax.
Grim Tales, Spellcasting game mechanics; Copyright 2003, Benjamin R. Durbin, published by Bad Axe Games, LLC.
Grim Tales, Horror game mechanics; Copyright 2003, Benjamin R. Durbin, published by Bad Axe Games, LLC.
Grim Tales, Firearms game mechanics; Copyright 2003, Benjamin R. Durbin, published by Bad Axe Games, LLC.
Grim Tales, Vehicle game mechanics; Copyright 2003, Benjamin R. Durbin, published by Bad Axe Games, LLC.
Grim Tales, Cyberware game mechanics; Copyright 2003, Benjamin R. Durbin, published by Bad Axe Games, LLC.
Grim Tales, Copyright 2004, Benjamin R. Durbin, published by Bad Axe Games, LLC
Grim Tales, Mass Combat game mechanics; Copyright 2004, Benjamin R. Durbin, published by Bad Axe Games, LLC.
Grim Tales, Crystalline Technology game mechanics; Copyright 2004, Benjamin R. Durbin, published by Bad Axe Games, LLC.
Slavelords of Cydonia, Copyright 2004, Matthew Beall, Eric Tam, and Benjamin R. Durbin, published by Bad Axe Games, LLC.

Grim Tales uses its own variation of the d20 rules, hence the many references to different books. Since I'm only copying the rules for Lethids, I think this could be cut down to the sources relevant to that, but I don't know what they are. I assume that the relevant books are Possessors: Children of the Outer Gods, Grim Tales, and Slavelords of Cydonia, but without a full text comparison I can't be sure. (This is one of the more annoying aspects of the OGL, sadly.)

Anyway, the rules for lethids are in Appendix B. This is divided into several sections, only some of which are strictly rules related.

The first section is "the lethid campaign", which explains the origin, physiology, and psychology of the lethid. The name is derived from aboleth, as these are aboleth variants (although the text doesn't explain their relationship to the aboleth from the core rules, if any), and probably a play on illithid since the lethid are apparently supposed to be OGC substitutes for that monster we can't use (at least not without giving up our copyrights to DM's Guild).

The lethid are basically the sentient shadows of a Lovecraftian deity created when it brushed against our plane. They have your typical plot to take over the world using their evil means. They don't have a hive mind, per se, but they do share a single will that allows them to coordinate harmoniously. Rarely a lethid might go crazy and need to be put down by its fellows.

Cydonia is a post-apocalyptic pulp setting. In it's history, the lethid were at least partly responsible for the fall of Atlanis (which was ruled by the serpentfolk sli'ess) and other horrific events in Earth's history.

They're your typical evil flying seafood from space with dark designs on the world and humanity. Not much else I can say about them.

The second section is "lethid abilities", which introduces the OGC rules that I can now quote without fear of legal repercussions.

Lethid Abilities
Implant
The lethid are parasitic creatures that devour the brains (and thoughts) of intelligent creatures. Two subraces of lethid in particular, the nihileth and rgleth, similar in appearance and physiology, are physically adapted to this purpose. To this list one may add the tiny, burrowing mohldaleth, which control their hosts from within.
Both nihileth and rgleth are squid-like in appearance, with six tentacles: four grasping tentacls, and two implantation tentacles. The nihileth is more advanced mentally, with a larger brain and weaker tentacles; while the rgleth is more physically robust, with a smaller brain and longer, more powerful grasping tentacles.
The nihileth and mohldaleth prefer to prey on the major humanoid races, while rgleth tend to control combat capable animals and powerful beasts of burden. Lethid can also implant themselves into aberrations, dragons, giants, humanoids, magical beasts and monstrous humanoids of the proper size and intelligence level (see table below). Each possesses a special attack that allows it to implant itself into a target creature’s nervous system, and a corollary ability, unhost. (Mohldaleth have a separate ability, burrow, that allows them to actually penetrate the flesh of their victims to travel undetected within the host body.)

Lethid Subrace	Size Threshold	Int Threshold
Mohldaleth	at least 3 sizes larger (Medium or larger)	6 or more
Nihileth	1 - 3 sizes larger (Medium - Huge)	6 or more
Rgleth	1 - 4 sizes larger (Medium - Gargantuan)	2 or less

• Implant (Ex): To use this ability, a nihileth or rgleth must first establish a hold by successfully grappling a creature with one of its grasping tentacles. If the lethid begins its turn with a hold on the creature, it can try to attach its two implantation tentacles with a single grapple check. The lethid gets a +2 circumstance bonus to this check for every grasping tentacle that it has attached beyond the first.
  (Mohdaleth have a corollary set of abilities, latch and burrow, detailed in their individual description below.)
  If the nihileth or rgleth begins a round with its two implantation tentacles attached to a creature, it can attempt to graft itself to its victim’s nervous system. The victim must succeed at a DC 25 Will save.
  Creatures failing their Will save who fall within the size and intelligence thresholds of the attacking lethid are transformed into a hosted nihileth or rgleth (see the template below)—the implanted lethid now has complete control of the victim’s mind and body.
  Creatures outside the attacking lethid’s control thresholds suffer 1d4 damage and 2d4 Wisdom damage (Fortitude save DC 18 halves Wis damage) when a nihileth or rgleth uses its implanation tentacles to attack.
  Nihileth prefer hosts from the major humanoid races and rgleth prefer predatory animals, but each can implant themselves into aberrations, dragons, giants, humanoids, magical beasts, and monstrous humanoids. Nihileth can only implant themselves into creatures with a single head and brain and a permanent intelligence score of at least 6. Rgleth can only dominate creatures with an Intelligence score or 2 or less.
  A hosted lethid intertwines itself so closely to the host creature’s vital organs that the two are effectively a single creature with a single hit point total. Consequently, it is impossible to simple cut a hosted nihileth or rgleth free from its host without killing the host, or even to damage the lethid parasite without damaging the host. If a nihileth or rgleth separates from its host, divide the total damage dealt to the templated creature equally between the lethid and its host; this may leave one or both of the creatures dead or dying.
• Unhost (Ex): A nihileth or rgleth can unhost itself from the creature to whom it is attached as a full-round action, which does not provoke attacks of opportunity. A lethid that is feeling particularly malevolent (as is usually the case) can attempt to kill its host by destroying its nervous system as it departs (see below).

Removing a Lethid
Removing a hosted lethid without killing the host is difficult although not impossible. A nihileth or rgleth may voluntarily decide to unhost (see above). A heal, limited wish, or remove disease spell will force the lethid to make a Fortitude save (DC 5 + caster level) or be ejected from the host's body; a wish or miracle will automatically eject it. Note that all of these effects must first overcome the lethid's spell resistance.
It is also possible to remove a lethid through mundane means (such as pulling or cutting the lethid from the host) but at significant risk to the host. A hosted lethid can only be removed through mundane means if it is unconscious or dead. Removal of a dead lethid requires a DC 25 Heal check (and the Surgery feat).
For a hosted lethid that is merely unconscious, any amount of continuous electrical shock will automatically disrupt its hold on the host and allow a Surgery check (DC27) to remove and kill it. A conscious lethid may be removed through surgery if it is somehow incapacitated for the entire duration of the surgery, such as by a hold monster spell.
If a living or dead lethid is forcefully removed from a creature, even by delicate surgery, there is a chance of catastrophic brain damage. The host must make a Death From Massive Damage Fortitude save (DC20); allow a +1 bonus to this check for each point by which surgeon's skill check exceeded the Surgery DC. Failing this save leaves the host forever comatose; the brain stem is damaged or destroyed. Success means that the host survived, but may still suffer from long-term physical or psychological effects at the GM's discretion.
Freed hosts are rarely the creatures they were previous to their infestation. Though victims often recall very little, they usually suffer dark and terrifying nightmares for the remainder of their days. Some hosts retain a strange insight into the world of their former captors, but they are not eager to speak about their visions.

Psionics
The lethid are powerful mentalists. Each subrace possesses one or more of the following spell-like or supernatural abilities, as noted in its stat block. The DC for these abilities are based on the attacking lethid's Charisma modifier, and the effects are resolved at a caster level equal to the lethid's HD. Lethid do not have to roll caster level checks to activate these abilities nor do they suffer spell burn.
Aphasic Hammer [Sp]
Range: Medium
Will save (DC13 + Cha modifier) negates
The lethid can project a 30 ft. radius burst of psionic energy that renders all creatures within it unable to speak or form coherent vocal utterances for 1d10 minutes. A creature afflicted in this way can be cured by dispel magic, heal, or any magical effect that can cure insanity or aphasia. This is a mind-affecting effect. This ability is equivalent to a 3rd-level spell effect.
Blast of Discord [Sp]
Range: 0
Will save (DC13 + Cha modifier) negates
Some lethid can emit a powerful blast of mental energy which leaves all creatures within a 30 ft. radius confused for 2d4 rounds. Lethid (and creatures hosting or under the mental control of a lethid) are immune to this effect. This is a mind-affecting effect. This ability is equivalent to a 3rd-level spell effect, but it may not be dispelled once a creature has been affected.
Greater Blast of Discord [Sp]
Range: 0
Will save (DC14 + Cha modifier) negates
All intelligent creatures within a 30 ft. radius of the lethid must make a Will save or be confused for 3d4 rounds. This is a mind-affecting effect. This ability is equivalent to a 4th-level spell effect, but it may not be dispelled once a creature has been affected.
Phase Mastery [Su]
This lethid has mastered the ability to shift between dimensions, as if it were under the effect of a blink spell. It can begin or end this effect as a move-equivalent action which does not provoke an attack of opportunity. Once every 3 rounds, a lethid with phase mastery can also use plane shift as a spell-like ability, effective caster level 9th. The lethid may only use this ability to shift itself (or its willing or unwilling targets) between the Prime Material Plane and the lethid dimension.
Presence Leech [Sp]
Range: 60 feet (Sp):
Will save (DC14 + Cha modifier) negates.
Some lethid can attempt to siphon the psychic energy from one creature with an Intelligence score of 6 or greater within 60 feet. The target must succeed at a Will save (DC equal to 14 + Cha modifier) or suffer 2d4 points of temporary Charisma damage. This temporary Charisma damage lasts 1 hour. If the attack succeeds, the lethid gains an enhancement bonus to its Charisma equal to the damage dealt for 1 hour. This is a mind-affecting effect. This attack is equivalent to a 4th-level spell.
Ray of Disruption [Sp]
Range: Medium
Fortitude save (DC16 + Cha modifier) for half
The lethid can launch a focused wave of matter-disrupting psionic energy at a single target within range. The lethid must make a successful ranged touch attack to affect a creature with this ability, which deals (HD+2) d6 points of disruption damage. This attack has a critical threat range of 19-20. If used against an object, the wave ignores its hardness. Any creature or object reduced to 0 or fewer hit points by this attack is completely dissolved into an incoherent jumble of dust and ooze. This ability is equivalent to a 6th-level spell effect.
Synaptic Avalanche [Sp]
Range: 60-foot cone
Will save (DC15 +Cha modifier) negates (see below)
This psionic attack is an overwhelming flood of mental stimulus that affects all intelligent creatures within a 60 ft. cone. Creatures caught in its path must succeed at a Will save or suffer 1d6 points of Wisdom damage and become stunned for 3d6 rounds. Creatures must subtract their Intelligence modifier from their saving throw roll against this attack (e.g. a character with an Intelligence score of 16 suffers a -3 penalty, whereas a character with an Intelligence score of 8 gets a +1 bonus). A successful save halves the Wisdom damage and negates the stunning effect. This is a mind-affecting effect. This ability is equivalent to a 5th-level spell, but it may not be dispelled once a creature has been affected.

Lethid Subtype Template/Traits
For GMs who wish to expand their campaign with their own lethid creatures, the lethid subtype definition is as follows:
Traits: A lethid possesses the following traits (unless otherwise noted in the creature's description).

• Amphibious—lethid can breathe both air and water; they can take 10 with Swim checks (even in stressful conditions) and can use the run action when swimming in a straight line.
• +4 racial bonus to Climb checks and a +2 racial bonus to Concentration, Listen, and Spot checks.
• +2 racial bonus to Will saves.
• +4 skill points per Hit Die.
• Lethid are vulnerable to electricity.
• Immune to disease and poison.
• Resistance to acid 5 and cold 5.
• Spell-like ability: At will—detect thoughts (DC equal to 12 + Cha modifier). Effective caster level equal to HD.
• Telepathy 100 ft.
• Lethid almost always also have the extraplanar, evil, and native subtypes.
• CR adjustment: +1.4

The next sections are the lethid bestiary entries. Here we learn of the subspecies of lethid, which are mohldaleth, nihileth, rgleth, shibboleth, and (true) aboleth.

The mohldaleth are burrowing parasites that enter a humanoid host and influence their behavior, so they work as spies, viziers, cult leaders and stuff. The nihileth are flying octopuses that engulf a humanoid host's head and control their body, who serve as lieutenants in the hierarchy. The shibboleth are giants who control large numbers of small animals, which they uses as spies on civilization. The rgleth are similar to the nihileth, but they only take large animals as hosts and thus serve a brute force role. The true aboleth are the most powerful and act as leaders; they're basically aboleths but with even greater powers, like their slime turning victims into living zombies.

Here are the rules for the mohldaleth and its hosts. I omitted the description between the statistics and combat section, as they didn't seem rules related.

Mohldaleth
Diminutive Aberration (Evil, Extraplanar, Lethid, Native)

Hit Dice:	3d8 (19 hp)
Initiative:	+8
Speed:	20 ft. (4 squares), swim 30 ft., fly 10 ft. (good)
Armor Class:	20 (+4 size, +5 Dex, +1 natural), touch 19, flat-footed 15
Base Attack/Grapple:	+2/-15
Attack:	Bite +11 melee (1d2-5)
Full Attack:	Bite +11 melee (1d2-5)
Space/Reach:	1 ft./0 ft.
Special Attacks:	Blast of discord, burrow, insinuate, attach, psionics, unhost
Special Qualities:	Amphibious, damage reduction 5/magic, darkvision 60 ft., evasion, immunity to poison and disease, lethid traits, resistance to acid 5 and cold 5, spell resistance 18, telepathy 100 ft., vulnerability to electricity
Saves:	Fort +2, Ref +8, Will +7
Abilities:	Str 1, Dex 21 , Con 12, Int 16, Wis 15, Cha 16
Skills:	Climb +6, Concentration +9, Hide +27, Knowledge (the planes) +6, Knowledge (arcana) +6, Listen +12, Sense Motive +8, Move Silently +15, Spellcraft +9, Spot +12, Swim +6
Feats:	Alertness, Improved InitiativeB, Weapon Finesse
Environment:	Aquatic, urban
Organization:	Solitary, pair, cadre (3-15)
Challenge Rating:	4
Treasure:	None
Allegiances:	Always Leth-Thol'Zad, evil, lethid
Advancement:	4 HD (diminutive), 5-6 HD (tiny)

Combat
Unhosted mohldaleth never engage opponents in direct confrontations, as their psionic powers are quite limited. When detected, they almost always attempt to flee, employing their deadly burrow attack only if faced with a very small group of enemies. On occasion, mohldaleth act as assassins for their lethid masters. If on such a mission, a mohldaleth attempts to latch onto its mark when it is unknown, latching onto it unnoticed and killing it by burrowing through its heart or brain.
More frequently, a mohldaleth is on the hunt for a host, carefully scouting potential targets and employing its mind-reading psionics to find a host with a compatible disposition. It will attempt to burrow into its target unnoticed, so that the latter does not even know that it has been infected. Ideally, a mohldaleth implants itself into the host when it is sleeping, sealing the tiny entry wound with its cure minor wounds ability. A host infested in this manner will have little indication of the evil it carries besides a vague recollection of strange dreams on the previous evening and a sensation of vitality. Things may change when it starts hearing the dark voices in its head...

• Evasion (Ex): A mohldaleth takes no damage if it makes its save against an attack that normally deals half damage on a successful Reflex save.
• Attach (Ex): Any creature at least 3 sizes larger than the mohldaleth is suitable prey. A mohldaleth can latch itself to other creatures with its mouth and tentacles, flattening its body to make removing it very difficult. To use this ability, a mohldaleth must succeed at a melee touch attack. If it succeeds, it has latched itself to the target and gains a +6 cover bonus. Any successful melee or grapple attack against a latched mohldaleth causes it to lose its grip.
• Burrow (Ex): A mohldaleth that begins a round latched to an opponent can burrow into it with a successful bite attack. The target creature loses any Dexterity and dodge bonuses to AC for this attack.
  A burrowed mohldaleth has total concealment (50% miss chance) and gains a cover bonus equal to the host's total AC bonus +4 (not including Dexterity, dodge, or shield bonuses if the host is not trying to avoid the attack). A successful hit deals half damage to the host and half to the mohldaleth; an attack that misses the mohldaleth due to concealment deals its damage to the host. A spellcaster must have line of sight or have some other means of detecting its precise location to affect a mohldaleth with a targeted spell. An attacker can reduce a burrowed mohldaleth's concealment to 20% and gain line of sight by making a DC 20 Spot check.
  If a mohldaleth begins a round burrowed in a host, it can attempt to insinuate itself into the creature (see below), or it can attempt to kill the creature instantly by burrowing through its heart or brain as a full-round action. Treat this as a coup de grace attack that deals 4d4 points of damage instead of critical damage with its bite attack and does not provoke attacks of opportunity.
• Insinuate (Ex): A mohldaleth that begins a round burrowed in a creature can automatically graft itself to its victim's nervous system and use it as a host (see below). This is a full-round action. The host must immediately make a DC 20 Will save or its attitude toward the mohldaleth improves by two steps. If the host's attitude is already helpful, then it loses its two lowest allegiances and gains allegiances to Leth-Thol'Zad, evil, or lethid. A mohldaleth host cannot take any new allegiances other than Leth-Thol'Zad, evil, or lethid. It must make another DC20 Will save at the beginning of each week it serves as a mohldaleth host until it is either freed of its influence or gains the insinuated allegiances.
  As mohldaleth do not dominate the minds of creatures they insinuate into, they must rely on stealth, preparation, and telepathic persuasion to convince their hosts to act according to their desires. A mohldaleth typically influences its host subtly by accessing its host's innermost wishes and desires and then planting its dark whispers and insinuations in the host's subconscious.
  It is possible for a direct conflict to occur between a host's will and a mohldaleth's insinuations, leading to psychological disorders. (See Hosting a Mohldaleth below.)
  Mohldaleth prefer hosts from the major humanoid races, but they can implant themselves into aberrations, dragons, giants, humanoids, magical beasts, and monstrous humanoids that are three or more size categories larger. Mohldaleth can only insinuate into creatures with a single head and brain and an Intelligence score of at least 6.
  A hosted mohldaleth burrows towards the base of the skull, underneath the skin and muscle of a humanoid host. It implants its tentacles so deeply into the host's brain and spinal cord that tearing it out would kill the host immediately. (See Removing a Hosted Lethid above.)
• Psionics (Sp): All mohldaleth have the following abilities, usable at will—clairvoyance, clairaudience, cure minor wounds, detect chaos, detect evil, detect good, detect thoughts, hypnotism (DC 14), nondetection, sleep (DC 14); 3/day—suggestion (DC 16); 1/ day—telekinesis (DC 18). In addition, mohldaleth can employ the following lethid ability once per day: blast of discord (DC 16).
  A mohldaleth employs its psionic abilities at an effective caster level 7th. All of the save DCs are Charisma-based.
• Unhost (Ex): See description above.
• Vulnerability to Electricity (Ex): Electricity attacks cause 50% more damage to mohldaleth. A mohldaleth that suffers electricity damage in excess of its Constitution must make a Fortitude save (DC equal to damage dealt) or be stunned for 1d4 rounds.
• Saves: Mohldaleth get a +2 racial bonus to Reflex and Will saves.
• Skills: Mohldaleth have a +2 racial bonus on Concentration, Listen, and Spot checks. They have a +4 racial bonus to Hide and Move Silently checks and a +8 racial bonus to Climb and Swim checks. Mohldaleth can always take 10 on Swim checks, even in dangerous or distracting conditions. They can also use the run action when swimming in a straight line.

Hosting a Mohldaleth
Although a mohldaleth is a worm burrowed inside its host's head, it does not outright control its host as the other lethid. A creature hosting a mohldaleth does not acquire a template; a host and its lethid parasite remain two separate creatures.
Due to the mohldaleth's influence over its host, the two will often act in concert. The cruel baron hosting a mohldaleth will likely come to revel in the power and evil offered by his parasite and will fiercely resist any efforts to dislodge it. Oftentimes, when the mohldaleth is subtle, it will insinuate itself into a host without its knowledge and patiently warp its mind over time. A hosted mohldaleth is able to constantly read its host's thoughts, and as a result the DC of any mind-affecting abilities it employs against the host is increased by +4.
Because a mohldaleth does not completely dominate the mind of its host, it is possible a direct conflict occurs between a host's will and a mohldaleth's insinuations, leading to psychological impairment. This is more likely if the mohldaleth has infested a creature who holds incompatible allegiances. Such conflicts force the mohldaleth host to succeed at a DC 17 Will save or be dazed for 1 d4 rounds (the save DC is based on the base mohldaleth's Charisma). The host gets a +2 circumstance bonus to this save if it is aware that it has been infested by a mohldaleth.
New Abilities
The host gains the following psionic abilities that it may use 3 times per day each: detect thoughts, enthrall. A mohldaleth host also gains darkvision 60 ft.
Combat
In combat, the host and the mohldaleth act as two independent creatures and they make separate initiative rolls. The host can uses its skills, attacks, and powers normally, and the mohldaleth can also act each round on its own initiative. Obviously, the mohldaleth is limited by location of its host, but can otherwise employ any of its psionic powers or spell-like abilities.

So the mohldaleth fills a similar niche as the puppeteer from the 3.x psionics rules, except that it's far more intelligent and doesn't have complete control over the host. This introduces roleplaying opportunities due to its ability to act on its own and potential schisms between the parasite and the host.

I'll post the nihileth, rgleth, shibboleth, and true aboleth later. After that, I'll post the rules for the sli'ess if anyone wants it. The next post will be about the nihileth and its origins, which are deeper than you would expect.

Feel free to ask me questions or offer legal advice.

 

[VelvetViolet]

And here's the statistics and abilities for nihileth:

Nihileth (Unhosted)
Small Aberration (Evil, Extraplanar, Lethid, Native)

Hit Dice:	6d8+6 (33 hp)
Initiative:	+2
Speed:	10 ft. (2 squares), swim 30 ft. , fly 15 ft. (average)
Armor Class:	17 (+1 size, +2 Dex, +4 natural), touch 13, flat-footed 15
Base Attack/Grapple:	+4/+8
Attack:	Tentacle +7 melee (1d3 plus poison)
Full Attack:	4 tentacles +7 melee (1d3 plus poison)
Space/Reach:	5 ft/5 ft.
Special Attacks:	Implant, unhost, poison, psionics
Special Qualities:	Amphibious, damage reduction 5/magic, darkvision 60 ft., immunity to poison and disease, lethid traits, resistance to acid 5 and cold 5, spell resistance 18, telepathy 100 ft., vulnerability to electricity
Saves:	Fort +3, Ref +4, Will +10
Abilities:	Str 10, Dex 14, Con 12, Int 18, Wis 16, Cha 17
Skills:	Climb +5, Concentration +12, Hide +15, Intimidate +12, Knowledge (the planes) +13, Knowledge (arcana) +13, Listen +14, Sense Motive +8, Move Silently +13, Spellcraft +9 (+11 scrolls), Spot +14, Swim +9
Feats:	Ability Focus (ray of disruption), Combat Casting, Improved GrappleB, Weapon Finesse
Environment:	Aquatic, Urban
Organization:	Solitary, pair, cadre (3-15)
Challenge Rating:	7
Allegiances:	Always Leth-Thol'Zad, evil, lethid
Advancement:	7-8 HD (Small); 9-12 HD (Medium); 13-18 HD (large)

Combat
An unhosted nihileth employs different tactics depending on whether it is actively hunting a host. If it is searching for a host, it will attempt to stun the most mentally powerful or charismatic member of its opponents with its psionics and then attempt to implant itself as quickly as possible. If it only wants to neutralize its opponents, then it will attempt to attack its opponents with its powerful psionic abilities from a distance, only using its tentacles and devastating implant/ unhost combination if it is forced into close combat or if it has incapacitated all of its opponents with its psionics.

• Unhosted nihileth get a +4 racial bonus to grapple checks.
• Implant (Ex): See description above.
• Unhost (Ex): See description above.
• Poison (Ex): Contact, Fortitude DC 16, initial and secondary damage 1d6 Wis. The save is Wisdom-based.
• Psionics (Sp): All nihlleth have following abilities, usable at will—charm monster (DC 17), detect thoughts (DC 15), dimension door, hypnotism (DC 14), levitate. In addition, a nihileth has the phase mastery ability (DC 18) and can also employ each of the following lethid psionic abilities once every 3 rounds: ray of disruption (8d6 damage, DC 21 Fort halves), presence leech (DC 17), synaptic avalanche (DC18).
  A nihileth uses all of its psionic abilities at effective caster level 9th. All of the save DCs are Charisma-based.
  Note: There are rumors of variant nihileth which possess slightly different psionic powers akin to those of the aboleth, shibboleth, or rgleth, including aphasic flare, greater blast of discord, and overstimulation. The GM may add these abilities or replace existing ones at his discretion.
• Vulnerability to Electricity (Ex): Electricity attacks deal an additional 50% damage to nihileth. In addition, an electricity attack that deals damage in excess of the nihileth's Constitution (12, unless hosted) forces it to make a Fort save (DC equal to damage dealt) or be stunned for 1d4 rounds.
• Skills: A nihileth has a +2 racial bonus on Concentration, Listen, Move Silently, and Spot checks, as well as a +8 racial bonus to Swim checks. It can always take 10 on Swim checks, even in dangerous or distracting conditions. It can also use the run action when swimming in a straight line.

The nihileth is essentially an open game content substitute for the ilithid. When hosted (engulfing its host's head), it resembles the stereotypical squid-headed humanoid. The nihileth serve as lieutenants to the aboleth and coordinate a number of other lethid under themselves.

The nihileth is perhaps the most interesting of the lethid, trivia-wise. It is modeled directly on the possessor from Possessors: Children of the Outer Gods. Possessors was originally available on RPGNow, but Ronin Arts took down all their books after the merger with OneBookShelf due to disputes with the terms of service or something. Anyway, the possessor was originally created as an open game content substitute for the ilithid. Although it has similar capabilities and fulfills the squid-headed humanoid cliche, it goes about it very differently: the possessor, as the name implies, possesses humanoid victims by engulfing their heads and puppeteering their bodies around (similarly to intellect devourers). They were later converted to PF1 in Forgotten Foes.

Although the nihileth and possessor are largely identical in capabilities (flying octopuses that engulf victims' heads), there are a few differences I noticed. The possessor has non-functional eyes and relies on blindsight, whereas the nihileth relies on darkvision but oddly its artwork depicts no visible eyes. The possessor drains the life from its host, killing them within hours, whereas the nihileth and rgleth don't seem to have the same effect.

It also shares its name with an undead aboleth variant, the nihileth from Kobold Press' Tome of Beasts. If one were to use both, then I would suggest renaming the parasitic form. I can't think of a name at present.

 

[VelvetViolet]

And here is the hosted nihileth template. Oddly, it is included in Grim Tales but not Slavelords of Cydonia.

(Oh, and I forgot to note that there are some instances where a lethid is stated to have fire resistance. This is an error and supposed to be cold resistance. I have edited this accordingly.)

Creating a Hosted Nihileth
“Hosted nihileth” is an acquired template that can be added to any aberration, dragon, giant, humanoid, magical beast, or monstrous humanoid of size Gargantuan or smaller that has a head and a single brain and an Intelligence score of at least 6.
A hosted nihileth uses all of a creature’s base statistics and abilities except as noted here.

• Size and Type: The creature’s type changes to aberration. Do not recalculate the creature’s base attack bonus, Hit Dice, saves, or skill points. It gains the extraplanar, evil, lethid, and native subtypes. Size is unchanged.
• Speed: If the base creature does not have a swim speed, it gains a swim speed equal to 2/3 its base land speed.
• Hit Dice: Same as the base creature plus those of the base nihileth. All other HD are unchanged.
• Armor Class: The base creature’s natural armor bonus improves by +2.
• Base Attack/Grapple: Add the BAB attack bonus for the base nihileth to the base attack bonus for the base creature. Hosted nihileth make all tentacle attacks as if they had Improved Grapple and Weapon Finesse.
• Attack: A hosted nihileth retains all the attacks of the base creature. It also gains four tentacle melee attacks (1d3 plus poison) that it can use as a primary attack.
• Full Attack: A hosted nihileth retains all the attacks of the base creature. It also gains 4 tentacle melee attacks (1d3 plus poison) that it can use as its primary attacks.
• Damage: The hosted nihileth’s tentacle attacks do 1d3 points of damage plus poison (no Str modifier).
• Special Attacks: A hosted nihileth retains all the special attacks of the base creature, and the special attacks and psionics of the nihileth. Hosted nihileth employ all of their psionic abilities at effective caster level 12th.
• Special qualities: A hosted nihileth has all the special qualities of the base creature, plus the following:
  • Damage reduction 5/magic.
  • Darkvision 60 ft.
  • Immunity to poison and disease
  • Resistance to acid 5 and cold 5
  • Spell resistance 18
  • Telepathy 200 ft.
  • Sensitivity to Electricity (Ex): An electricity attack that deals damage in excess of the nihileth’s Constitution forces it to make a Fort save (DC equal to damage dealt) or the hosted nihileth is stunned for 1d4 rounds.
  • Unhost (Ex): see description above.
• Saves: Add the base save bonuses of the base nihileth to the base save bonuses of the base creature. Hosted nihileth have a +2 racial bonus to Will saves.
• Abilities: A hosted nihileth retains the base creature’s original Strength, Dexterity, and Constitution scores. The hosted nihileth’s Intelligence, Wisdom, and Charisma scores become that of the base nihileth’s score +2, or that of the base creature, whichever is higher.
• Skills: A hosted nihileth retains all of the base creature’s skills, or the base nihileth’s ranks in Intelligence, Wisdom, or Charisma-based skills (whichever is higher). Hosted nihileth have a +2 racial bonus on Concentration, Listen, and Spot checks.
• Feats: Hosted nihileth attack with their tentacles as if they had the Improved Grab and Weapon Finesse feats. They also gain Combat Casting and Ability Focus in one of its psionic abilities (usually ray of disruption or presence leech).
• Environment: Same as the base creature and aquatic.
• Organization: Solitary, pair, cadre (3-15).
• Challenge Rating: Same as the base creature’s, modified by base nihileth’s HD: 6 HD to 8HD, +6; 9 HD to 11 HD, +8; 12-14 HD, +10; 15-18 HD, +12.
• Allegiances: Always Leth-Thol’Zad, evil, lethid.

So the 3.x rules don't seem the best for representing combined creatures. This method of possession is more complex rules-wise than the possessor or intellect devourer. To summarize: the nihileth has physically engulfed the host's head, grafted its implantation tentacles to the nervous system, and now controls the body, and has tentacles leftover it can use to make melee attacks.

If you want some freaky pictures of this process, then check out Possessors: Children of the Outer Gods.

Next up is the Rgleth, a parasitic lethid that attaches to the spinal column of a large animal and controls its body.

 

[VelvetViolet]

Here's the rgleth.

Rgleth
Small Aberration (Evil, Extraplanar, Lethid, Native)

Hit Dice:	4d8+8 (26 hp)
Initiative:	+9
Speed:	10 ft. (2 squares), swim 30 ft. , fly 10 ft. (good)
Armor Class:	18 (+1 size, +3 Dex, +4 natural), touch 14, flat-footed 15
Base Attack/Grapple:	+3/+8
Attack:	Tentacle +7 melee (1 d3+1 plus paralysis)
Full Attack:	6 Tentacles +7 melee (1d3+1 plus paralysis) and bite +4 melee (1d6+1)
Space/Reach:	5 ft./5 ft.
Special Attacks:	Burst of speed, constrict (1d3+1 plus paralysis), implant, improved grab, poison, psionics
Special Qualities:	Amphibious, darkvision 60 ft., damage resistance 5/magic, dimensional fetish, immunity to disease and poison, lethid traits, resistance to cold 5 and acid 5, telepathy 100 ft., vulnerability to electricity
Saves:	Fort +2, Ref +4, Will +7
Abilities:	Str 12, Dex 17, Con 12, Int 5, Wis 12, Cha 14
Skills:	Concentration +4, Climb +7, Hide +16, Jump +8, Listen +7, Move Silently +12, Spot +7, Swim +10, Tumble +10
Feats:	Improved GrabB, Improved Initiative, MobilityB, Weapon Finesse
Environment:	Aquatic, underground
Organization:	Solitary or group (5-10)
Challenge Rating:	5
Treasure:	None
Allegiances:	Always Leth-Thol'Zad, evil, lethid
Advancement:	5-6 HD (Small), 7-9 HD (Medium)

Combat
When not in their lair, rgleth are almost always out hunting for hosts. They typically stalk their prey, using cover to hide to the best effect, before surprising their victims and attempting to implant themselves as quickly as possible.
Rgleth avoid combat while unhosted. When confronted by a concerted attack, rgleth will either retreat or attempt to find the largest, fiercest animal available to use as a host.

• Rgleth have a +4 racial bonus to grapple checks.
• Burst of speed (Ex): Once every three rounds, a rgleth can move with phenomenal quickness, increasing its speed by 30 ft. during that round.
• Constrict (Ex): A rgleth deals 1d3+1 damage plus its poison with a successful grapple check.
• Dimensional fetish (Su): A rgleth with this ability is linked to a specific physical feature of the Prime Material Plane that it can use as a conduit for slightly longer forays to the lethid dimension. Roll 1d8 or choose from the following table to determine the rgleth's fetish:

1. Flat mirrored surfaces	5. Knots
2. Shadows	6. Book pages
3. Standing water	7. Smoke
4. Corners (inside vertices)	8. Circles

For a physical feature to count as a dimensional fetish, it must be a significant part of an object or area no smaller than 2 sizes smaller than the rgleth (or hosted creature). When within 5 feet of an object that matches its dimensional fetish, a rgleth can jump to the lethid dimension as a free action. This ability is identical to ethereal jaunt cast at 9th level, except it transports the rgleth to the lethid dimension and the rgleth must, at some point during the action, return through a location within 5 feet of an instance of its dimensional fetish, anywhere in this plane, no matter what the distance. This ability can only be employed as part of a move action.

• Implant (Ex): See description above.
• Improved grab (Ex): To use this ability, a rgleth must hit with a tentacle attack. It can then attempt to start a grapple as a free action. If it wins the grapple check, it establishes a hold and can constrict.
• Paralysis (Ex): A rgleth's tentacles are coated with a contact sedative that slows its prey's reflexes. A creature hit or grappled by a rgleth's tentacles must make a DC 14 Fortitude save or be paralyzed for 2d4 rounds. A rgleth that has implanted itself into a creature can inject an antidote into its nervous system, which immediately removes all penalties dealt by the rgleth's sedative. The save DC is Constitution-based.
• Psionics (Sp): A rgleth can employ several psionic abilities. At will—clairaudience, daze (DC 12), detect thoughts (DC 14). The save DCs are Charisma-based. Effective caster level 7th.
• Unhost (Ex): See description above.
• Vulnerability to electricity (Ex): Electricity attacks deal an additional 50% damage to rgleth. In addition, an electricity attack that deals damage in excess of the rgleth's Constitution forces it to make a Fortitude save (DC equal to the damage dealt) or be stunned for 1 d4 rounds.
• Skills: Rgleth have a +2 racial bonus on Concentration, Listen, Move Silently, and Spot checks. An unhosted rgleth's chameleon-like skin gives it a +4 racial bonus to Hide checks.

A rgleth has a +8 racial bonus to Swim checks. It can always take 10 on Swim checks, even in dangerous or distracting conditions. It can also use the run action when swimming in a straight line.

Creating a Hosted Rgleth
Any creature that falls victim to a rgleth’s implant attack immediately becomes a hosted rgleth. The creature’s voluntary brain functions are supplanted by those of the rgleth.
A hosted rgleth uses all the base creature’s statistics and special abilities, except as noted here:

• Size and Type: The creature’s type becomes aberration. Do not recalculate its Hit Dice, base attack bonus, saves, or skill points. It loses any alignment or allegiance subtypes. Size is unchanged.
• Hit Dice and Hit Points: Current and future Hit Dice remain those of the base creature.
• Armor Class: Increase the base creature’s natural armor bonus by +1.
• Base Attack/Grapple: Add the rgleth’s base attack bonus to the base creature’s base attack bonus, and include the rgleth’s +4 racial bonus to grapple to the hosted creature’s grapple bonus.
• Attack: The hosted rgleth retains the base creature’s primary attacks.
• Full Attack: The hosted creature retains the base creature’s primary and secondary attacks and gains two tentacle attacks as secondary attacks.
• Damage: The hosted rgleth’s tentacles do damage equal to the base rgleth’s tentacle damage plus 1/2 the hosted rgleth’s Strength modifier plus paralysis.
• Special Attacks: A hosted rgleth retains all the special attacks of the base creature except for spells and spell-like abilities. It also gains a number of psionic and extradimensional abilities. The save DC for these abilities is 10 + 1/2 hosted rgleth’s HD + Cha modifier, unless otherwise noted.
• Blast of discord (Sp): See description above. It can use this ability 3 times per day.
• Paralysis (Ex): A hosted rgleth retains its paralysis attack.
• Psionics (Sp): A hosted rgleth can employ several psionic abilities. At will—clairaudience, daze, detect thoughts. Effective caster level 9th.
• Special Qualities: The hosted rgleth retains all of the base creature’s special qualities and gains the following:
  • Darkvision 60 ft.
  • Dimensional fetish (Su): A hosted rgleth retains the rgleth’s dimensional fetish ability (see rgleth entry).
  • Overstimulation (Ex): A hosted rgleth can push its body beyond normal natural limits for short bursts of time. The hosted rgleth gains +4 to Strength, +4 to Constitution, and +5 ft. to speed for a number of rounds equal to its Hit Dice. A hosted rgleth is dazed for the next round after its overstimulation ends. A hosted rgleth can begin or end overstimulation as a free action on its turn. It can overstimulate a number of times per day equal to its Con modifier.
  • Sensitivity to electricity (Ex): A hosted rgleth that suffers an electricity attack that deals damage in excess of the hosted rgleth’s Constitution must make a Fortitude save (DC equal to damage dealt) or be stunned for 1d4 rounds.
  • Telepathy 100 ft.
  • Unhost (Ex): See description above.
• Saves: The hosted creature retains the base creature’s Fortitude and Reflex saves. Substitute the base rgleth’s base Will save. Hosted rgleth have a +2 racial bonus on Will saves.
• Abilities: Increase the base creature’s Strength by +2 and Dexterity by +2. Replace the base creature’s Intelligence, Wisdom, and Charisma scores with the base rgleth’s scores.
• Skills: The base creature retains all of its skills and racial skill bonuses and gains the base rgleth’s ranks in the latter’s Intelligence, Wisdom, and Charisma-based skills. Hosted rgleth have a +2 racial bonus to Concentration, Listen, and Spot checks.
• Feats: The hosted rgleth gains Alertness and Improved Initiative.
• Challenge Rating: Same as base creature +2.
• Advancement: Same as base creature and base rgleth.
• Allegiances: Always Leth-Thol’Zad, evil, lethid.

To summarize: the rgleth attaches to the host animal's spine, injects stimulants, and feeds on its host to boost its own nervous reserves. The hosted rgleth may use its psychic powers and tentacles in tandem with its hosts's attacks. They serve as brute muscle in the lethid hierarchy.

What's perhaps most interesting about the rgleth is its characteristic dimensional fetish ability. Subject to the fetish restriction, the rgleth can essentially teleport not unlike a blink dog or phase spider.

If the mohldaleth may be seen as loosely analogous to the puppeteer, the unhosted nihileth (and rgleth) to the intellect devourer, and the hosed nihileth to the mind flayer, then the hosted rgleth is loosely analogous to the displacer beast. I guess?

The original possessor was capable of possessing both animal and humanoid targets, but this was split between the lethids into the nihileth and rgleth. The Possessors book depicts a possessor engulfing the head of a quadrupedal creature, whereas the rgleth attaches to the spine.

And that's it for the parasitic lethids. The rest are free-living and rely on their mind-altering slime to control victims. Next up is the Shibboleth, and finally the True Aboleth. That should be coming tomorrow.

 

[VelvetViolet]

And here's the Shibboleth:

Shibboleth
Huge Aberration (Evil, Extraplanar, Lethid, Native)

Hit Dice:	16d8+32 (104 hp)
Initiative:	+4
Speed:	15 ft. (3 squares), swim 40 ft.
Armor Class:	21 (-2 size, +2 Dex, +11 natural), touch 10, flat-footed 19
Base Attack/Grapple:	+12/+35
Attack:	Slam +17 melee (2d6+7 plus 2d4 acid plus disease)
Full Attack:	5 slams +17 melee (2d6+7 plus 2d4 acid)
Space/Reach:	15 ft./10 ft.
Special Attacks:	Acid, constrict 2d6+7 plus 2d4 acid, disease, greater blast of discord, improved grab, psionics, spray
Special Qualities:	Damage reduction 10/magic, darkvision 60 ft., frightful presence, immunity to poison and disease, lethid traits, psychic puppets, resistance to cold 5 and acid 10, spell resistance 24, telepathy 100 ft., vulnerability to electricity
Saves:	Fort +9, Ref +7, Will +19
Abilities:	Str 25, Dex 14, Con 15, Int 19, Wis 24, Cha 20
Skills:	Bluff +19, Climb +17, Concentration +26, Gather Information +24, Intimidate +16, Knowledge (history) +20, Knowledge (local) +22, Knowledge (the planes) +18, Listen +25, Move Silently +17, Sense Motive +21, Spot +25, Swim +17
Feats:	Alertness, Combat Casting, Combat Reflexes, Great Fortitude, Improved GrappleB, Improved Initiative, Psionic Focus (illusion)
Environment:	Aquatic, underground
Organization:	Solitary
Challenge Rating:	14
Allegiances:	Always Leth-Thol'Zad, evil, lethid
Advancement:	17-20 HD (Huge), 21 -30 HD (Gargantuan)

Combat
A single shibboleth can control hundreds of creatures, usually of the one or two species with which the shibboleth is most familiar. Any living creature with a nervous system and an Intelligence score of 2 or lower that comes into contact with a shibboleth's ooze is affected as by a disease (DC 20 Fort save). Once infected, a creature suffers from Shibboleth Mind Rot until its Intelligence reaches 0, at which point the creature dies and its body becomes a psychic puppet under the control of the shibboleth.
Vermin are immediately affected by the shibboleth's ooze because of their simple brain structure. A vermin exposed to the ooze must make a DC 27 Fort save or become a psychic puppet instantly.
A vermin that failed its Fortitude save, or an infected creature whose Intelligence score reaches 0, may become a psychic puppet if it dies is within 20 miles of a willing shibboleth. The shibboleth can keep an animated body "alive" for months by nourishing it with its ichor before it rots away. Shibboleth will often use swarms of vermin to defend itself and its lair.
A shibboleth's diseased ooze only affects creatures with Intelligence scores of 2 or less—although it can affect higher animals whose Intelligence score has temporarily fallen to 2 or less (as a result of the shibboleth's feeblemind ability, for example).
A shibboleth can control up to 10 times its HD in psychic puppets.

• Acid (Ex): A shibboleth's body secretes acid that dissolves only flesh. Any melee hit or constrict attack inflicts 2d4 points of acid damage.
• Constrict (Ex): A shibboleth inflicts 2d6+7 slam damage and 2d4 acid damage with a successful grapple check.
• Disease (Ex): Any time a creature comes into physical contact with a shibboleth, its secretions, or one of its minions, it must make a Fortitude save (DC 20) or contract shibboleth mind rot. Creatures with an Intelligence score of 3 or more are immune to the shibboleth's disease.
• Improved Grab (Ex): To use this ability, a shibboleth must hit with a tentacle attack. As a free action, it can then start a grapple without provoking an attack of opportunity. If it wins the grapple check, it establishes a hold and can constrict.
• Psionics (Sp): A shibboleth is a powerful psionicist. Shibboleth have the following psionic abilities, usable at will: detect thoughts (DC 17), hypnotic pattern (DC 18), illusory wall (DC 20), mirage arcana (DC 21), misdirection (DC 18), programmed image (DC 22), project image (DC 23). It can psionically crush its opponents' minds, as per feeblemind (DC 20), 3 times per day.
  In addition, a shibboleth can employ the lethid psionic ability greater blast of discord (DC 19) 3 times per day.
  The save DCs for its psionics are Charisma-based. Effective caster level 12th.
• Psychic Puppets (Su): A shibboleth can control up to 10 times its Hit Dice worth of creatures that have succumbed to its mind rot. This ability has a 20-mile range.
  Taking control of or giving a command to such a creature is a free action for the shibboleth.
  A shibboleth has a telepathic link with its psychic puppets that allows it to use the puppets' senses as though they were its own. The shibboleth's complex alien intelligence allows it to process information through any number of puppets simultaneously without difficulty. The controlling shibboleth can treat a single psychic puppet it designates as its psionic conduit as an extension of its body for the purpose of determining the range of its psionic abilities, as long as it is within 1 mile. It may only designate a new psionic conduit once per hour, even if the current psionic conduit is incapacitated, dies, or leaves the shibboleth's range.
  A shibboleth will often control hundreds of creatures simultaneously, usually vermin, and have several vermin swarms guarding its lair at all times. Shibboleth have been known to control packs of dogs, dire animals, and humanoids they have afflicted with feeblemind.
• Spray (Ex): Once every 3 rounds, a shibboleth can spray a 30 ft. cone of diseased, acidic ooze. The ooze inflicts 8d6 acid damage and exposes all creatures who take damage from this attack to shibboleth mind rot disease. Creatures caught in the attack make a DC 20 Reflex save to take half damage. The save DC is Constitution-based.
• Vulnerability to Electricity (Ex): Electricity attacks deal an additional 50% damage to shibboleth. In addition, an electricity attack that deals damage in excess of the shibboleth's Constitution forces it to make a Fort save (DC equal to damage dealt) or be stunned for 1d4 rounds.
• Skills: Shibboleth have a +2 racial bonus on Concentration, Spot, Listen, and Move Silently checks.
  A shibboleth has a +8 racial bonus to Swim checks. It can always take 10 on Swim checks, even in dangerous or distracting conditions. It can also use the run action when swimming in a straight line.
  Shibboleth have a +4 racial bonus to grapple checks.

Shibboleth Mind Rot
Disease:
A psionic brain-wasting disease spread by shibboleth.
Infection:
Contact with a shibboleth's ooze by touching an infected creature or through a shibboleth's Spray attack. This disease only affects creatures whose Intelligence score is 2 or less at the time of exposure, as well as living creatures lacking an Intelligence score, such as vermin. Successful successive saving throws do not allow creatures to recover normally from the disease unless their Intelligence is greater than 2 (but does prevent damage). An infected creature with an Intelligence score less than 2 can only recover normally if it is farther than 20 miles of the infecting shibboleth.
Fortitude DC:
DC20 (Infected creatures with an Intelligence score greater than 2 receive a + 7 bonus to their saving throws. Vermin must save against DC 27). A creature that successfully saves is immune to shibboleth mind rot for the next 24 hours.
Incubation Period:
12 hours.
Damage:
1d6 Intelligence plus a second saving throw or 1 point of the damage is permanent. When an infected creature's Intelligence reaches 0, that creature is dead (its brain is now ooze) and its body subject to use as a psychic puppet for a willing shibboleth within 20 miles.
A sentient creature converted to a psychic puppet often shows outward signs, such as a jerkiness or stiffness of motion, slurring of speech, etc. It can be detected by making an opposed Sense Motive check against the shibboleth's Bluff. The shibboleth suffers a -1 penalty to its check for every mile that separates it from its puppet.

Creating a Shibboleth Psychic Puppet
Once a creature has succumbed to shibboleth mind rot, it becomes a psychic puppet that is completely under the shibboleth’s control. If that shibboleth dies, so too do all its puppets.
A sentient creature converted to a psychic puppet often shows outward signs, such as a stiffness of motion, slurring of speech, etc. It can be detected by making an opposed Sense Motive check against the shibboleth’s Bluff check. The shibboleth suffers a -1 penalty to its check for every mile that separates it from its puppet.

• Size and Type: The creature’s type becomes aberration. Do not recalculate Hit Dice, base attack bonus, saves, or skill points. It loses any allegiance subtypes. Size is unchanged.
• Special Attacks: A psychic puppet retains all of the special attacks of the base creature except for class abilities, spells, spell-like abilities, psionics, and abilities that require an Intelligence score.
  • Disease (Ex): A psychic puppet is a carrier of shibboleth mind rot. Creatures who make any physical contact with this creature or its carcass must make an immediate Fortitude saving throw or contract the disease. A creature need only make one successful save per 24 hours no matter how many times it is exposed to the disease. This disease ability applies in addition to any other disease ability the base creature normally possesses.
• Special Qualities: The psychic puppet retains all of the base creature’s special qualities that do not require an Intelligence score. Psychic puppets gain the following special qualities:
  • Darkvision 60 ft.
  • Immunity to poison and disease
  • Psionic conduit (Su): The controlling shibboleth can treat a psychic puppet within 1 mile as an extension of its body for the purpose of determining the range of the shibboleth’s psionic abilities. A shibboleth can only select a new psionic conduit once per hour, even if the existing one is killed or incapacitated.
  • Resistance to acid 5
  • Sensitivity to electricity (Ex): A psychic puppet that suffers electricity attack that deals damage in excess of its Constitution must make a Fort save (DC equal to damage dealt) or be stunned for 1d4 rounds.
  • Shibboleth dependency (Ex): The psychic puppet dies if its controlling shibboleth dies or if the shibboleth is more than 20 miles away.
• Saves: The puppet retains the base creature’s Fortitude and Reflex saves. Substitute the controlling shibboleth’s total Will save.
• Abilities: A psychic puppet retains the base creature’s ability scores, except that it has no Intelligence score. Psychic puppets are immune to all mind-affecting effects.
• Skills: Psychic puppets cannot use skills with Intelligence as their key ability. It retains all of the base creature’s other skill ranks.
• Feats: The puppet retains all feats except those related to Intelligence-based skills or abilities.
• Environment: Same as the controlling shibboleth.
• Organization: Solitary (shibboleth often use single spies), group (5-10), or plague (11-50, when gathered by the controlling shibboleth and depending on creature type).
• Challenge Rating: Same as base creature.
• Allegiances: —
• Advancement: Same as base creature.

The shibboleth is an aboleth subrace characterized by their unique slime. Whereas the standard aboleth's slime causes its victims to become aquatic, the shibboleth's slime rots the brain of low-Int victims and turns them into its zombie-like puppets who can further spread the disease.

Next up is the True Aboleth, whose slime has the same effect on more intelligent beings.

 

[VelvetViolet]

And last but far from least, the true aboleth:

True Aboleth
Gargantuan Aberration [Evil, Extraplanar, Lethid, Native]

Hit Dice:	18d8+126 (207 hp)
Initiative:	+5
Speed:	10 (2 squares), swim 60, fly 20 (good)
Armor Class:	18 (-4 size, +1 Dex, +11 natural), touch 7, flat-footed 17
Base Attack/Grapple:	+13/+41
Attack:	Tentacle +21 melee (2d6+12 plus slime)
Full Attack:	6 tentacles +21 melee (2d6 +12 plus slime)
Space/Reach:	20 ft./10 ft.
Special Attacks:	Aura of horror, constrict (2d6+12 plus slime), discorporating rend, improved grab, maddening gaze, psionics, slime
Special Qualities:	Amphibious, damage reduction 10/magic and cold iron, darkvision 60 ft. , immunity to disease, poison, and acid, lethid traits, resistance to fire 10 and cold 10, spell resistance 32, spray, telepathy 1 mile, vulnerability to electricity
Saves:	Fort +15, Ref +9, Will +22
Abilities:	Str 34, Dex 13, Con 24, Int 23, Wis 24, Cha 25
Skills:	Bluff+28, Concentration +30, Decipher Script +24, Intimidate +28, Knowledge (arcana) +27, Knowledge (the planes) +27, Knowledge (religion) +27, Listen +32, Sense Motive +28, Move Silently +22, Spellcraft +29, Spot +32, Swim +32
Feats:	Ability Focus (ray of disruption), Alertness, Combat Casting, Great Fortitude, Improved Grapple, Improved Initiative, Iron Will, Lightning Reflexes, Quicken Spell-Like Ability (mass suggestion), Quicken Spell-Like Ability (greater teleport)
Environment:	Aquatic or underground
Organization:	Solitary, pair, cadre (3-5)
Challenge Rating:	18
Treasure:	Double standard
Allegiances:	Always Leth-Thol'Zad, lethid, evil
Advancement:	19-26 HD (Gargantuan); 27-34 HD (Colossal)

Combat
True aboleth are brilliant strategists, fanatically devoted to advancing the profound evil of Leth-Thol'Zad. The true aboleth's main strength is their immense mental power. An aboleth will rarely directly confront a threat or potential prey, instead preferring to use its illusions and mind-affecting abilities to lure and confuse enemies. When the enemy is vulnerably or in disarray, an aboleth will attempt to subjugate potentially useful creatures and simply kill or torture those that are not.
If true aboleth encounter a combat situation, they are almost certain to have prepared for it by coordinating their positions and lethid underlings, as well as readying a battery of defensive illusions and protective effects. When combat actually ensues, they prefer to remain in the back ranks, launching their psionic powers from a distance. True aboleth always begin by attempting to enslave humanoid opponents, employing mass suggestion and dominate person to turn the tables or lure victims forward into their slimy embrace. But they will not hesitate to just reduce impertinent enemies to sludge with their more directly destructive powers. They are more wary of spell casting opponents, and generally will target them first.

• Constrict (Ex): With a successful grapple check, a true aboleth deals 2d6 damage, plus its slime.
• Disrupting Rend (Su): A true aboleth disrupts matter it grasps with its tentacles by shifting portions of the target to extra-dimensional space. If a true aboleth successfully hits an opponent with at least two tentacles, the opponent suffers an additional 12d6 points of disruption damage (Fort DC 26 for half). Any creature or object reduced to 0 or fewer hit points by this damage is completely dissolved into an incoherent jumble of dust and ooze. A target can only be affected by the disrupting rend once per round. The save DC is Charisma-based.
• Psionics (Sp): At will—blink, clairaudience, clairvoyance, confusion (DC 21), cure moderate wounds, detect good, detect law, detect magic, detect thoughts (DC 19), greater dispel magic (DC 23), displacement, dominate person (DC 22), feeblemind (DC 22), hypnotic pattern (DC 19), illusory wall (DC 21), greater invisibility, quickened mass suggestion (DC 23), mirage arcana (DC 22), nondetection (DC 20), programmed image (DC 23), project image (DC 24), scrying (DC 21), telekinesis (DC 22), greater teleport, true seeing, unholy blight (DC 21); 3/day—prismatic spray (DC 24), wall of force.
  In addition, true aboleth can employ the following lethid psionic abilities at will: aphasic hammer (DC 20), ray of disruption (DC 25), presence leech (DC 21), synaptic avalanche (DC 22).
  True aboleth employ all of their psionic abilities at effective caster level 18th. The save DCs are Charisma-based.
• Improved Grab (Ex): To use this ability, a true aboleth must hit with a tentacle attack. It can then attempt to start a grapple as a free action. If it wins the grapple check, it establishes a hold and can constrict or use its disrupting rend.
• Slime (Ex): The true aboleth secretes a sticky, diseased slime from every part of its body that is corrosive to nonliving matter. The slime deals 2d6 damage to wood, metal, and stone on contact. Successfully striking a true aboleth with a melee weapon exposes the weapon to the slime, and a melee hit by a true aboleth will corrode armor or clothing. This slime also sticks to the skin of any creature that is hit in melee or grappled by a true aboleth, forcing it to make a DC 22 Fortitude save or contract true aboleth's mind fire disease. This save is required each round until the slime is wiped or washed off (requires a standard action).
• Spray (Ex): Once every 3 rounds, an aboleth can spray a 15-ft. cone of fluid, consisting of a mixture of acid and diseased slime. The slime inflicts 9d6 acid damage and showers its victims with the true aboleth's diseased slime. Creatures caught in the attack make a DC 26 Reflex save to take half damage. Creatures who fail their Reflex save are exposed to the diseased slime and must make a Fortitude save each round against the aboleth's mind fire. The save DC is Constitution-based.
• Utter Thralls (Su): A true aboleth can control up to 10 times its Hit Dice worth of creatures that have succumbed to its mind fire. This ability has a 50-mile range.
  Taking control of or giving a command to such a creature is a free action for the true aboleth, which it can use at anytime. An utter thrall acts on its own initiative count.
  A true aboleth has a telepathic link with its utter thralls that allow it to use the thrall's senses as though they were its own. The true aboleth's complex alien intelligence allows it to process information through any number of thralls simultaneously without difficulty. The controlling true aboleth can treat a single utter thrall it designates as its psionic conduit, acting as an extension of its body for the purpose of determining the range of its psionic abilities. This ability has a range of one mile. It may only designate a new psionic conduit once per hour, even if the current psionic conduit is incapacitated, dies, or leaves the aboleth's range.
  A true aboleth will often control dozens of thrall simultaneously and have several lesser lethid on hand to take orders.
• Vulnerability to Electricity (Ex): Electricity attacks deal an additional 50% damage to true aboleth. In addition, an electricity attack that deals damage in excess of the true aboleth's Constitution forces it to make a Fort save (DC 10 + damage dealt) or be stunned for 1d4 rounds.
• Skills: A true aboleth has a +2 racial bonus on Concentration, Listen, and Spot checks, as well as a +8 racial bonus to Swim checks. It can always take 10 on Swim checks, even in dangerous or distracting conditions. It can also use the run action when swimming in a straight line.

True Aboleth Mind Fire
Disease:
A psionic disease spread by true aboleth that weakens creatures' will and leaves them under their thrall.
Infection:
Contact with the psychic slime produced by either a true aboleth or an infected utter thrall. This disease only affects creatures capable of holding allegiances. Successful successive saving throws do not allow creatures to recover normally from the disease unless they are more than 50 miles from the aboleth that infected them; infected creatures can only otherwise be cured by magical or psionic means.
Fortitude DC:
DC22. Creatures with an allegiance to good gain a +2 bonus to their save roll, while creatures with an allegiance to evil suffer a -2 penalty to their save roll.
Incubation Period:
1 day.
Damage:
1 d4 Wisdom damage plus a Will save (DC 17) or one point of the damage is permanent Wisdom drain, and the victim becomes enchanted with the true aboleth. This effect is the same as a charm monster spell cast by the true aboleth, except that it has a range of 50 miles and a duration of 24 hours.
When an infected creature's Wisdom reaches 0, its brain is reduced to sludge and the creature's mind is destroyed. At this time, if the creature is within 50 miles of the true aboleth that infected it, the psychic energy infusing the creature's body keeps it alive as the true aboleth's utter thrall (see creature template). A creature in this state is only technically living. Curative spells such as heal are ineffective at this point. A successful dispel magic (against caster level equal to the true aboleth's HD) will release the creature from the true aboleth's thrall, but the creature will die immediately. Only a wish, miracle, or true resurrection will return the creature to normal at this point.

Creating a True Aboleth Utter Thrall
When a creature infected with a true aboleth's mind fire reaches 0 Wisdom, it is immediately converted to an utter thrall, absolutely under the control of the true aboleth that infected it.
"True aboleth utter thrall" is an acquired template that can be added to any creature with single brain, native physiology, and an Intelligence score of at least 3.
An utter thrall uses all of a creature's base statistics and abilities except as noted here.

• Size and Type: The creature's type becomes aberration. It loses any alignment/allegiance subtypes. It uses the base creature's statistics except as noted below.
• Speed: Reduce all of the base creature's speeds by 5 ft. (minimum speed 10 ft.). If the base creature can fly, its maneuverability rating drops to clumsy.
• Base Attack: An utter thrall's base attack bonus becomes equal to 3/4 its Hit Dice.
• Attacks: An utter thrall retains all of the base creature's natural weapons and manufactured weapon attacks, as well as weapon proficiencies. It gains a slam attack.
• Damage: An utter thrall deals damage from its natural and manufactured weapon attacks normally. Its slam damage depends on its size (use the base creature's slam damage if better): Fine: 1; Diminutive: 1; Tiny: 1; Small: 1d3; Medium: 1d4; Large: 1d6; Huge: 1d6; Gargantuan: 2d6; Colossal: 2d8. An utter thrall's slam attack also inflicts its slime on opponents.
• Special Attacks: An utter thrall loses all of the base creature's special attacks that are class abilities, psionic abilities, activated supernatural abilities except breath weapons, and psionic and spell-like abilities. An utter thrall also gains the following special abilities:
  • Psychic lament (Su): An utter thrall emits a continuous, maddening drone as side effect of its condition. All creatures (except lethid and those controlled by lethid) who approach within 60 feet of an utter thrall must make a DC 12 Will save or be affected as by a confusion spell for 1d4 rounds. The DC increases by +1 for each other utter thrall within 60 feet (up to a maximum of +10) of the creature attempting the save. This is a sonic mind- affecting effect. A creature that successfully saves cannot be affected by any other utter thrall's psychic lament until the next round. The save DC is Wisdom-based.
  • Slime (Ex): An utter thrall secretes a sticky, diseased slime from every part of its body that is corrosive to nonliving matter. The slime deals 2d6 damage to wood, metal, and stone. Successfully striking an utter thrall with a melee weapon exposes the weapon to the slime, and a hit from an utter thrall's natural weapon or slam attack will corrode armor or clothing. This slime also sticks to the skin of any creature that is hit by an utter thrall's natural weapon or slam attack, forcing it to make a DC 22 Fortitude save or contract mind fire disease, until the slime is wiped or washed off (requires a standard action).
• Special Qualities: An utter thrall retains all of the base creature's special qualities except class abilities and abilities that require activation. An utter thrall gains the following special qualities:
  • Aboleth dependency (Ex): An utter thrall immediately dies if its controlling true aboleth dies or is ever more than 50 miles away.
  • Damage reduction 5/slashing
  • Darkvision 60 ft.
  • Immunity to disease, death, mind-affecting, paralysis, poison, sleep, and stunning effects.
  • Immune to critical hits, non-lethal damage, fatigue, exhaustion, and Wisdom and Charisma damage.
  • Psionic conduit (Su): As long as the utter thrall is within 1 mile, the controlling true aboleth can treat one of its utter thralls as an extension of its body for the purpose of determining the range of its psionic abilities. A true aboleth can only designate one of its utter thralls as a psionic conduit at any time and it can change its selection once per hour, even if its current psionic conduit dies.
  • Resistance to acid 5
  • Sensitivity to electricity (Ex): A psychic puppet that suffers electricity attack that deals damage equal or greater to its total Hit Dice must make a Fort save (DC equal to 10 + damage dealt) or be stunned for 1d4 rounds (an utter thrall is not immune to this stunning).
  • Utter thralls suffer a -2 racial penalty to initiative rolls.
• Saves: An utter thrall retains the base creature's base Fortitude save bonus. Its Reflex save bonus becomes +1/3 HD and its base Will save bonus becomes +1/2 HD + 2. Utter thralls have a +2 racial bonus to Will saves.
• Abilities: An utter thrall's Dexterity decreases by 2, its Wisdom becomes 10, and its Charisma becomes 1. It has no Intelligence score.
• Skills: An utter thrall has no skills.
• Feats: An utter thrall loses all of the base creature's feats. It gains Great Fortitude and Toughness.
• Environment: Aquatic or underground
• Organization: Solitary, group (5-10), or plague (11 -50, when gathered by the controlling aboleth and depending on creature type).
• Challenge Rating: 1/2 HD
• Treasure: Half standard.
• Allegiances: —
• Advancement: Same as base creature.

The true aboleth is basically a giant aboleth whose slime turns its victims into zombies.

Although it's called the "true" aboleth, the text doesn't make any comparisons with the aboleth in the MM/SRD. The true aboleth is interchangeably referred to as an aboleth by the text. If I had to invent a connection, then I would say the standard aboleth is an immature form of the true aboleth... or maybe rename the true aboleth to something less confusing.

And that's all the lethid from Grim Tales and Slavelords of Cydonia. If anybody asks, then I can also post the rules for the sli'ess, their enemies.