jmartkdr2
Hero
So my suggestion for solving the most common case of 'recall lore' ruining an encounter is - don't use trolls. Or at least don't use trolls with the expectation that figuring out how to get past regeneration will be difficult but not too difficult. Trolls are just a poorly designed monster if you think of them that way.
That's for a few reasons: player are likely to know the weakness anyways, so if you force the pc's to not know you're forcing the player to metagame. And metagaming is bad. Trolls don't really give clues about what will work. They're not ice- or water- or plant-themed, so weakness to fire is either already known or would require a blind guess. It isn't obvious. Nor is it even something you could deduce from the description. Acid is just right out. The only clue you have is regeneration in general, and that obviously leads to fire, since it also works on hydras and most other things that regenerate.
So either the player gets to guess - in which case they'll get it immediately or not at all - or you call the player's out for metagaming and force them to metagame differently.
Now, trolls are decent bruisers if you use them as such (ie like you would ogres), so you can still include them, but just assume the players/pc's knowing how to deal with regeneration is factored in to the CR. Because it is.
The other creatures with specific weaknesses are all built this way as well. You wouldn't penalize player for thinking to use holy water against a vampire, would you? But vampires are built to assume the plc's will try to use at least of their weaknesses.
That's for a few reasons: player are likely to know the weakness anyways, so if you force the pc's to not know you're forcing the player to metagame. And metagaming is bad. Trolls don't really give clues about what will work. They're not ice- or water- or plant-themed, so weakness to fire is either already known or would require a blind guess. It isn't obvious. Nor is it even something you could deduce from the description. Acid is just right out. The only clue you have is regeneration in general, and that obviously leads to fire, since it also works on hydras and most other things that regenerate.
So either the player gets to guess - in which case they'll get it immediately or not at all - or you call the player's out for metagaming and force them to metagame differently.
Now, trolls are decent bruisers if you use them as such (ie like you would ogres), so you can still include them, but just assume the players/pc's knowing how to deal with regeneration is factored in to the CR. Because it is.
The other creatures with specific weaknesses are all built this way as well. You wouldn't penalize player for thinking to use holy water against a vampire, would you? But vampires are built to assume the plc's will try to use at least of their weaknesses.