A river troll is a distinct and infamous breed of troll that lives almost exclusively within dirty rivers, marshes and other foul waters, hence their name. They have fish-like fins on their heads and back.
A river troll somewhat resembles the bottom of the river, if that riverbed is particularly coated in sediment, slime, rotting vegetation, fish carcasses, and various other smelly detritus whose precise nature and origin are too horrible to contemplate. In all probability the river troll’s stink is even worse than that of the riverbed, since one can add the troll’s personal miasma to the ill-omened mélange of odors emitted from the mucky smears on its skin.
They often antagonize lizardfolk and any humanoid that gets too close to their river.
River trolls are infamous for their rather disgusting ability of puking acidic bile on their enemies.