Jörmungandr also known as the Midgard Serpent or World Serpent, is an unfathomably large and monstrous sea serpent or worm who dwells in the world sea, encircling the Earth and biting its own tail, an example of an ouroboros. As a result of his surrounding Midgard, the beast is referred to as the World Serpent. Jörmungandr releasing his tail is one of the signs of the beginning of Ragnarök.
