Scientific name -- Canis fenris
Size -- 550 lbs.
Diet -- deer, cattle, gods

The original Fenrir (of which these monsters are just the offspring) was the product of Loki and the giantess Angrboda. The gods raised the wolf in Asgard, but only Tyr had the courage to feed it. Unfortunately, the wolf grew larger and larger until nothing could chain him down. Finally the dwarves made a chain out of the roots of a mountain, silence of a moving cat, and the breath of a fish. In order to trick Fenrir into moving close enough to be chained, Tyr offered him food, and in retribution, the wolf bit off his arm. Fenrir then began to howl until the gods stuck a sword in his mouth as a gag.

At Ragnarok, Fenrir is fated to break his chains and kill Odin.