The coming of Ragnarok
Ragnarok is the cataclysmic event described in Viking mythology where the nine worlds that make up the cosmos are destroyed. It is a prophecy about the end of the world.
What Will Happen?
Ragnarok will begin when the wolf, Fenrir, son of Loki, breaks free of his imprisonment. This will lead to a chain reaction of events including the Midgard snake Jormungand rising from the sea and a wolf devouring the sun. Everything will come to a head in a huge battle that draws in the Gods, men and all the races of the nine worlds.
All these events were prophesied by the Allfather, Odin who had hung himself from the world tree, Yggdrasill for nine days so that he died and would be re-born with wisdom and foresight. The wisdom acquired by Odin allowed him to see the events of Ragnarok enabling him to plan for the end of the world, including rounding up all the Vikings heroes who died in battle to Valhalla, his great hall where they would feast and wait for the end of the world and the battle to end all battles.