In Norse mythology, Fenrir—the wolf who breaks free at Ragnarok—is the son of Loki.
Fenrir is one of Loki’s three monstrous children with the giantess Angrboða. His siblings are Jörmungandr, the Midgard Serpent, and Hel, ruler of the underworld. The gods become alarmed by the children’s powers and the prophecies surrounding them.
The gods attempt to restrain Fenrir with several bindings. He breaks the first two, but the dwarfs create the nearly weightless magical fetter Gleipnir, which holds him until Ragnarok. Fenrir’s captivity is therefore a major part of the events leading to the final battle.
At Ragnarok, Fenrir escapes and kills Odin. Odin’s son Vidar then avenges him and kills Fenrir. Fenrir should not be confused with Hati or Sköll, the wolves associated with pursuing the Sun and Moon.