Jormungandr (ヨルムンガルド?) also known as Midgardsomr (ミドガルズォルム?), is a demon in the series.
One of Loki's children. Jormungandr (also called the midgardsomr) was a snake that was so big that it would sleep on the bottom of the oceans across the whole world. Odin, accompanied by a giant tried to kill Jormungandr but he failed. Jormungandr will be on the side of chaos during ragnarok and will not survive it. (ragnarok is supposed to be the last war between order and chaos, in Northern mythology and after ragnarok a new world will be born from the remains of the old world.)
A two-handed sword created by upgrading Tyrfing through synthesis. When Loki, Fenrir, or Hel's friendship level is above Linked by Fate, Loki gives a 40% magic based effect, Fenrir gives a 40% ice based effect, and Hel a 40% ice based effect.
DemiKids Light & Dark
"A colossal demon living in the sea, who just keeps growing and growing."