The monstrous wolf destined to devour Odin at Ragnarök is Fenrir, also called Fenrisúlfr.
Fenrir is one of the three famous children of Loki and the jötunn Angrboða; his siblings are Hel and Jörmungandr. The gods recognize that the rapidly growing wolf will become dangerous, so they trick him into accepting the magical fetter Gleipnir. Týr places his hand in Fenrir’s mouth as a pledge and loses it when the wolf discovers that the gods intend to keep him bound.
At Ragnarök, Fenrir breaks free and joins the forces opposing the gods. In the Prose Edda’s account, he swallows Odin during the final battle. Odin’s son Víðarr then avenges him by forcing open the wolf’s jaws and killing him. The Poetic Edda also foretells that a wolf will kill Odin, while Snorri’s prose identifies that wolf as Fenrir.
Fenrir is often mixed up with Sköll and Hati, wolves associated with pursuing the sun and moon. Garmr is another monstrous canine figure linked with Ragnarök, but the wolf specifically connected with Odin’s death is Fenrir.