<P> In Norse mythology, Jörmungandr (Old Norse: Jǫrmungandr, pronounced (ˈjɔrmuŋɡandr̥), meaning "huge monster"), often written as Jormungand, or Jörmungand and also known as the Midgard Serpent (Old Norse: Miðgarðsormur), or World Serpent, is a sea serpent, the middle child of the giantess Angrboða and 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 it was able to surround the earth and grasp its own tail . As a result, it received the name of the Midgard Serpent or World Serpent . When it releases its tail, Ragnarök will begin . Jörmungandr's arch - enemy is the thunder - god, Thor . It is an example of an ouroboros . </P> <P> The major sources for myths about Jörmungandr are the Prose Edda, the skaldic poem Húsdrápa, and the Eddic poems Hymiskviða and Völuspá . Other sources include kennings in other skaldic poems . For example, in Þórsdrápa, faðir lögseims, "father of the sea - thread", is used as a kenning for Loki . There are also image stones from ancient times depicting the story of Thor fishing for Jörmungandr . </P>

Which child of loki is so large that it encircles the earth