Ragnarök, or the “reckoning of the gods,” is a terrible battle to end the Norse gods. This is detailed in Völuspá, a prophecy given to Odin by an unnamed Seeress. This story has heavy parallels to Christian Armageddon.
Ragnarök is signaled by the fimbulwinter, a winter lasting for three consecutive years. The golden rooster in Asgard crows and is matched by the crowing of a soot-black one in Helheim. Jörmungandr releases his grasp on his tail, causing all the bonds in the world to break, which frees Fenrir and Loki from imprisonment. It also frees Garm, a wolf who guards the hall of Helheim. Heimdall blows the Gjallarhorn, preparing the gods for war, including all the chosen warriors in Valhalla. The fire-jötnar of Muspellheim break free from the earth and attack the Aesir. Joining them are the wild beings of Jötunheim and the dead from Helheim. Loki is amongst them, steering the ship Naglfar, which is made of nail clippings from the deceased.
The two forces clash. Fenrir swallows Odin, who is then killed by Viðar. Jörmungandr kills Thor. Loki and Heimdall fall at each other’s blades. Freyr is killed for lack of a sword. The moon and sun are swallowed by the wolves that chased them across the sky. The world burns, crumbles, and plunges into darkness. Niðhogg rises from the ground and flies over the wreckage.
A new world is born. (According to Snorri, this world is ruled over by an unnamed supreme deity.) Baldr returns from Helheim and joins the few gods that survive. They find a golden chessboard lying in a field. Hœnir draws lots for prophecy, and a new, shining hall is built, called Gimlé.
Norse Pagans have many different ideas for how to interpret Ragnarök, given its depressing implications. For some, Ragnarök represents a difficult change, such as large cultural shifts and uprisings, or something cyclical. For others it’s the one time the gods massively screwed up. For others still, it’s a story potentially inspired by an ancient volcanic eruption that happened in Iceland and made its way into oral tradition. And for others still, Ragnarök is genuinely the Heathen version of the end-times.
There’s no consensus on how we should view Ragnarök. Ultimately, this is left for the individual to decide.