Jormungandr was born in Jotunheim to Loki (father) and a Jotun sorceress, Angrboða (mother). He is the second child of Loki; Fenris is his only full sibling. Although he was bullied and ostracized, Jormungandr grew up relatively happy on Asgard until Odin wiped Asgard’s memories and separated Loki’s children. Since then, Jormungandr lived alone in Alfheim’s only swamp until Odin died and the curse broke.

Freed from the curse, Jormungandr shapeshifted to an Asgardian form and met Sleipnir. Together, they wound up in Sakaar, where they were forced to battle. Though he had no prior experience, Jormungandr quickly learned how to hold his own alongside his brother. Initially at odds, Jormungandr’s relationship with his brother grew stronger after he accidentally bit Sleipnir when trying to bite the Hulk. Sleipnir survived the venom, and they escaped to Asgard. There, they found Asgard in ruins with their half-sister, Hela, attacking Surtur. Jormungandr found Fenris hanging on the cliffside and rescued his younger brother. Together, Sleipnir brought them all to the Afterlife, where they resided until after the threat of Thanos passed.

Always distrustful, Jormungandr is known to hold grudges and refuses to let others past his hard exterior. He’s been scorned one too many times and figures it's easier to push everyone away rather than endure the eventual pain and backstabbing. Due to being alone most of his life, Jormungandr lacks good manners and social skills. He often voices complaints in a brash, blunt way or says inappropriate things at the worst times. He is also quick to lose his temper, evidenced by lashing out at those who offend or hurt him. Jormungandr’s anger at Odin led him to vow a violent death on his grandfather. However, despite his tough, cold personality, he is very protective and has learned to let some people close. He will do anything to undo the wrongs that fell upon him and his siblings, especially if it involves punching his way through problems.

Jormungandr is a natural-born survior. He is self-taught to defend himself and boasts the strength and speed to hold his own in a battle. He prefers to use harsher methods that utilize his strength to overpower his opponents. He lacks a fighting style, instead of using whatever suits him at the moment, although he does prefer to use a battle-axe as his weapon of choice. He can also manipulate his size and shapeshift. When he is in his serpent form, Jormungandr possesses lethal venom that can kill any opponent with a single, fatal bite.