In Norse mythology, Fenrir is a giant wolf, the son of the trickster god Loki and the giantess Angrboða. Fenrir’s strength was so great that the gods became fearful of what he might do in the future. The gods, knowing of a prophecy that said Fenrir would eventually bring about the death of Odin, the chief of the gods, decided to take action to prevent this from happening. To contain him, the gods fashioned an unbreakable magical fetter called Gleipnir. When Fenrir was bound by this chain, he grew enraged and bit off the hand of the god Tyr, who had volunteered to place his hand in Fenrir’s mouth as a show of good faith. The gods then imprisoned Fenrir in a cave, where he would remain until the time of Ragnarök, the prophesied end of the world, when he would break free and kill Odin in a final battle.