Trolls are one of Gaea's flesh-peoples, made from the same living stock as humans, giants, and the beastmen. Like the rest of that family they breed with it, which is the only reason trollkin exist at all: a troll and a human can get a child between them, whatever either people thinks of the result. What Gaea poured into the troll was bulk and appetite and not much beyond that. They are large, slow-witted, and brutish, colored brown to green, and they eat other humanoids when they can run them down.