The Mountain Troll is a minor antagonist in Harry Potter and the Philosopher's Stone. He was let into Hogwarts School of Witchcraft and Wizardry on Hallowe'en of 1991 by Quirinus Quirrell, possessed by Tom Marvolo Riddle, in an attempt to steal the Philosopher's Stone of Nicolas Flamel.
Quirinus Quirrell was able to control this troll, a rare talent. He said later that he had a gift with trolls. He also used a troll to help protect the Philosopher's Stone.
Role in the film