Stone-giants

Mighty creatures of the Misty Mountains, and perhaps elsewhere in Middle-earth. The only known reference to them occurs in The Hobbit, in which Bilbo and the Dwarves encounter them as they cross the Misty Mountains. During a storm, the Stone-giants emerge, and cast huge boulders about a rocky valley as part of a bizarre game.

The difficulty of fitting Stone-giants (and all giants, for that matter) into Tolkien's world has led some to see the Stone-giants as a metaphor for crashing thunderbolts, or something similar. However, the detail of the Stone-giants' description, and the occurrence of other giants in Tolkien's work, makes it seem likely that these creatures actually did exist in Middle-earth.