History
Jormungand is a mythical, giant serpent/monster that, according to Norse Mythology, lives at the bottom of Yggdrasil, the World Tree, where he is curled around Midgard (Earth). When Jack asks Julie if this means he is wrapped around Earth, Alex points out that this is just a myth. The same myth also states that when Ragnarok occurs, Jormungand will rise up to consume the world and devour Thor.
When Loki, along with Hrymer and Amora the Enchantress successfully tricked Power Pack into stealing the Golden Apples of Idunn for him, thus dooming all Asgardians to die of old age, he unintentionally triggered Ragnarok and awoke Jormungand. The Giant Serpent immediately rose up to Asgard, driving Loki's army of Frost Giants off and throwing a wrench in his plans. The Serpent battled Power Pack, Thor and the Pet Avengers, defeating all of them. Knowing the legend, Thor offered to accept his death if Jormungand promised to spare the others, to which Jormungand agreed. Not wanting to give up, Alex grabbed Mjolnir and attacked Jormungand, proving himself worthy of the power of Thor. Julie meanwhile figured out a way to get the apples back. At her suggestion, Thor destroyed the gems Loki had given Power Pack earlier, causing the de-aging spell of Amora to backfire against Loki, Amora, and Hrymer. With Loki turned into a baby, Julie was able to get the Apples back and stop Ragnarok. With Ragnarok averted, Jormungand retreated to the bottom of Yggdrasil to await the end of times.