When the chains of Loki and Fenrir break, then Ragnarok can begin. Three Years of continual winter will end with a battle of the gods, whereupon the giant Surt will use his flames to burn the world. Baldur will return from the land of the dead, and the world will be reborn, with Baldur to guide creation and bring about the return of the pantheons.
That's how it is supposed to be according to Odin, anyway. Loki apparently has other plans.
He's broken his chains early, and is preparing to start the End of the World. He's keeping his own council, but the Norse gods know he needs to free Fenrir no matter what form of Ragnarok Loki plans. Their counterplan is you; Loki knows where the anchors are to Fenrir's current set of chains. They want you to set up new anchors and keep Fenrir bound. They will attempt to contain Loki and hopefully rebind him while you work.