Bagpuss
Legend
And attacking trolls with fire… this is entirely the GM’s fault. Everyone knows that trolls are vulnerable to fire. If you’re the kind of GM who doesn’t want players to act on that knowledge, then don’t use trolls. Problem solved, simple as that.
Yeah if a significant number of people in this world where trolls are only folklore and not real, know that trolls need to be killed with fire, can you imagine how many would know in a world where trolls are a real risk if you travel too far from civilization. This is the sort of stuff most villagers would know, so of course adventurers would have picked up.