Trolls are big monsters who live in the dark and turn to stone if they are hit by sunlight. They were said to be made in mockery of Ents, just like Orcs were created in mockery of Elves. The 13 dwarves who travelled with Bilbo during his quest, were captured by three Trolls named Tom, Bert and Bill Huggins. They were tricked however and while they were discussing the way in which to cook their captives they forgot the sun was rising and they turned to stone. Frodo came by this place many years later and saw the three stoned trolls.