Jörmungandr (pronounced [ˈjœrmuŋɡandr]), mostly known as Jormungand or Jörmungand, the Midgard Serpent, Midgarðsormur, or World Serpent, is, in Norse mythology, a sea serpent, and the middle child of the giantess Angrboða and the god Loki. According to the Prose Edda, Odin took Loki's three children, Fenrisúlfr, 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. When he lets go the world will end. As a result he earned the alternate name of the Midgard Serpent or World Serpent. Jörmungandr's arch enemy is the god Thor.
Comment: swallowing his own tail is another serpent character.