Jörmungandr is a sea serpent in Norse mythology. He is the middle child of the god/jotun Loki and the giantess Angrboða. His full siblings are Fenrir and Hel.
Thor and Jörmungandr from the Altuna runestone at Altuna church, Enköpings municipality, Sweden
According to the myth, Odin took Loki's children. He tossed Jörmungandr into the ocean that surrounds Midgard. The serpent grew so big that he was able to surround the Earth and grasp his own tail, and as a result he earned the alternate name of the Midgard Serpent or World Serpent. Jörmungandr's arch enemy is the god Thor. It is said that both Thor and Jörmungandr will die fighting each other during Ragnarök.