1911 Encyclopædia Britannica/Fenrir

FENRIR, or Fenris, in Scandinavian mythology, a water-demon in the shape of a huge wolf. He was the offspring of Loki and the giantess Angurboda, who bore two other children, Midgard the serpent, and Hel the goddess of death. Fenrir grew so large that the gods were afraid of him and had him chained up. But he broke the first two chains. The third, however, was made of the sound of a cat’s footsteps, a man’s beard, the roots of a mountain, a fish’s breath and a bird’s spittle. This magic bond was too strong for him until Ragnarok (Judgment Day), when he escaped and swallowed Odin and was in turn slain by Vidar, the latter’s son.