Fenrir

In Norse mythology, Fenrir is a giant wolf-like beast that is one of the three children of the demon-god Loki. Fenrir is immense-- when he opens his jaws they fill up the sky. Fenrir was born small, but grew quickly in both size and in ferocity. This worried the gods, so they made a magical chain with which they would bind him. They had to trick him into being captured, and it cost the god Tyr his hand, but Fenrir was imprisoned. Years later, at the end of the world or Ragnarok, Fenrir finally escaped, and killed the leader of the gods, Odin, by swallowing him. Odin's son Vidar took his revenge and killed Fenrir by snapping his gigantic jaws.