(also Fenris, Fenriswolf)
The gods kidnapped Fenrir and brought him to Asgard where they could watch him carefully. He was so savage that only the war god Tyr dared to feed him. At Ragnarok, Fenrir was freed from captivity and swallowed Odin.
Learn more in John Lindow's Norse Mythology: A Guide to the Gods, Heroes, Rituals, and Beliefs.