Jörmungandr

In Norse mythology, Jörmungandr, often written Jormungand, or Jörmungand and also known as the Midgard Serpent or World Serpent, is a sea serpent, the middle child of the giantess Angrboğa and the god Loki. According to the Prose Edda, Odin took Loki's three children by Angrboða, the wolf Fenrir, Hel and Jörmungandr, and tossed Jörmungandr into the great ocean that encircles Midgard. The serpent grew so large that he was able to surround the earth and grasp his own tail. As a result, he received the name of the Midgard Serpent or World Serpent. When he lets go, the world will end. Jörmungandr's arch-enemy is the god Thor.