Here's something from a campaign I ran a while back. Fair warning: if the grendels get the drop on a party, they're much tougher than their CR would suggest.
Grendel Troll
Large Giant
Hit Dice 6d8+18 (45 hp)
Initiative +1 (Dex)
Speed 40', swim 30'
AC 19 (-1 Size, +1 Dex, +5 natural, +4 mage armor)
Touch AC 10
Flat-footed AC 18
BAB +4
Grapple +13
Attack Greatsword +9 melee (2d6+5), Longspear +5 ranged (1d8+5)
Full Attack Greatsword +9 melee (2d6+5), Longspear +5 ranged (1d8+5)
Space/Reach 5'/10' (20' with longspear)
Special Attacks Spell-like abilities
Special Qualities None
Fort +7
Ref +6
Will +8
Str 21
Dex 13
Con 16
Int 16
Wis 13
Cha 15
Skills: Climb +2, Concentration +10, Hide +5, Listen +2, Move Silently +5, Spellcraft +5, Spot +2, Survival +5
Feats: Great Fortitude, Iron Will, Lightning Reflexes
Environment Any land and underground
Organization Solitary, Pair, Coven (3-6)
CR 7
Treasure Double standard
Grendel trolls are similar to ogres, but much more intelligent, possessing powerful innate magical abilities. Adult grendels stand 9 to 10 feet tall and weigh 300 pounds or more. Their skin color is always gray or black. Their smooth, thick hides are typically covered with a stiff fur, gray or black (the opposite of their skin color). Grendels usually wear normal clothing, well kept and clean.
Grendels speak Common, Giant, and at least one other language.
COMBAT
Grendels rely on their spell-like abilities, resorting to physical combat only when necessary. Grendels prefer ambush to fair fights, and will not hesitate to retreat before superior forces. Grendels despise ogre mages and will often fight one to the death.
Spell-like abilities: These abilities are as spells cast by a 10th-level sorcerer, save DC 12 + spell level.
At will - Blur, Color Spray, Mage Armor, Ray of Enfeeblement, See Invisible
3/day - Cure Serious Wounds, Entangle, Melf's Acid Arrow
1/day - Bull's Strength, Cat's Grace, Ice Storm, Improved Invisibility, Slow, Stoneskin
Blur: 10 minutes, 20% miss chance
Bull's Strength: 10 minutes, 1d4+1 Strength
Cat's Grace: 10 minutes, 1d4+1 Dexterity
Color Spray: Range 50' (DC 13)
Cure Serious Wounds: 3d8+10
Entangle: 10 minutes, 40' radius spread (DC 13)
Greater Invisibility: 10 rounds
Mage Armor: 10 hours
Melf's Acid Arrow: 4 rounds, 2d4 (DC 14)
Ray of Enfeeblement: 1d6+5 Strength
See Invisibility: Range 200', 100 minutes
Slow: Range 50', 10 rounds, 10 creatures w/in 30' (DC 15)
Stoneskin: 100 points, 100 minutes
A grendel troll's favored class is sorcerer.
Edited to be 3.5 compatible.