Gleipnir

Gleipnir was the chain created by the Dwarves of Nidavellir that served to keep the Fenris Wolf chained until the advent of Ragnarok. Fenris Wolf was freed from Gleipnir thanks to the intervention of A.I.M. who suggested that being the the son of Loki, and knowing that Loki was a master shapeshifter, he too should be able to change shape like his father. To do this, the Fenris Wolf devoured one of the A.I.M. scientists and took his shape, and being that it's new human size was much smaller than its natural shape, the collar tied to Gleipnir managed to slip off.^[1]

When the Mangog attacked Asgardia, Jane Foster, the Mighty Thor, tied him up with Gleipnir, before tying the chains to Mjolnir and hurling the hammer into the Sun, taking the Mangog with it, destroying Mjolnir.^[2] Gleipnir or a part of it, was recovered by Loki. When Loki was attacked by Mánagarmr and rescued by Jane, now a Valkyrie, he gave her the chain in hopes to restrain the wolf.^[3]

Image	Description	Issue
	On Earth-23948, Loki broke Mjolnir's enchantment, stealing it from Thor and went on a killing spree to weaken Odin. Loki used Mjolnir to release the Fenris Wolf from Gleipnir, ultimately unleashing Ragnarök. Gleipnir was destroyed alongside the Nine Realms and reality itself by Surtur with the Twilight Sword.	What If...? Dark: Loki #1