Fenris or Fenrir is a monstrous wolf in norse mythology. He is the son of the trickster god loki and the giantess Angrboda. His siblings are Jormungar, the midgard serpent and Hel, the goddess of death. His sons are Sköll and Hati Hróðvitnisson, the wolves that chase the sun and moon across the sky.
When the god Odin saw his growing power he feared that he would overthrow the gods and ordered that he was imprisoned. So the god Tyr bound him on an island far far away where he lies to this day.
According to mythology at Ragnarok, the great war to end all wars, when the ground shakes he will be freed from the island and will march forward with Loki and his siblings to kill the gods. In this great battle, he will kill Odin but then his son Víðarr will avenge him and kill the wolf.