Quickleaf
Legend
For those who use trolls in your campaigns, do you even bother with the "can only be killed with fire/acid" deal? It's a cool facet of trolls, but PC's are bound to say "oh, well, we have torches and flint, no problem". Thoughts?
I do something different with trolls. They are fey oathkeepers, seeking any slip up to justify wanton and excessive retribution against the oath-breaker. True to the myth of the Green Knight, they are feared by monarchs, and also by fey warlocks.
Trolls IMC are gluttons, consuming 10 times the amount of food that a man would each day; a clan of trolls can quickly wipe out a region's livestock (not to mention villagers). One nasty way to kill a troll is to throw it in a pit and let it starve.
Another method is "salting" a troll; owing to their bond with the natural world (in days of old oaths were sworn under trees, hence the word "treow" which "troll" may have in part evolved from), trolls respond to salt like most plants - it kills their ability to regenerate. My world has "alchemical salts" which can be added to a single attack (coating a blade or used as spell component) to add the "salt" damage type. Salt has other applications with zombies, giant slugs, treants/dryads, etc.
Fire works against most trolls, but there are a few kinds which fire damage enables them to spawn minions which erupt from the troll's body like in Aliens. Think of how a pine cone needs intense heat to release it's seeds - "coniferous" troll tribes work that way.
Acid doesn't bypass regeneration, but in some cases I let it slow the regeneration down to a crawl, buying the PCs time for a more permanent solution.