Jormungandr

Jormungandr, the Midgard Serpent, is the middle child of Loki and the giantess Angrboda. Odin casts it into the deep sea, where it grows so vast it circles the whole world and grips its own tail. Twice it crosses Thor. When the god goes fishing with Hymir, he hooks the serpent and nearly drags it up before the line is cut; and at Utgarda-Loki's hall, Thor unknowingly lifts the disguised serpent as a great grey cat, raising one mighty paw. At Ragnarok the two meet for the last time: Thor crushes its head, then walks nine steps and falls dead from its venom.