In Norse mithology, Jörmungandr ( Old Norse Jǫrmungandr, pronounced [ˈjɔrmuŋɡandr]), often written Jormungand, or Jörmungand and also known as the Midgard Serpent (Old Norse: Midgarðsormr), or World Serpent, is a sea serpent, the middle child of the giantess Angrboða 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.