Ragnarok, the fate or doom of the gods, and by a later and probably mistaken reading their twilight, is the destruction of the world in Norse mythology, described chiefly in the Eddic poem Voluspa and systematised in Snorri Sturluson's Prose Edda. It is the most fully narrated eschatology surviving from any pre-Christian European tradition, and it is unusual among the world's eschatologies in that the gods lose.
The sequence is given in outline as follows. Moral collapse among human beings: an age of axes and swords, brothers killing brothers, no one sparing anyone. Then Fimbulvetr, the great winter, three winters following one another with no summer between them. The wolves swallow the sun and the moon. Yggdrasil shudders. The bonds break: Loki is loosed and the wolf Fenrir with him; the world serpent Jormungandr rises from the sea; the ship Naglfar, built of dead men's nails, is freed; Surt comes from the south with fire; and the giants and the dead advance over the rainbow bridge Bifrost, which breaks beneath them. Heimdall sounds the Gjallarhorn. Odin falls to Fenrir and is avenged by his son Vidar. Thor kills Jormungandr and dies of its venom after nine steps. Freyr falls to Surt, having given away his sword. Tyr and the hound Garm kill one another. Surt sets the world alight and the earth sinks into the sea.
And then it rises again, green, and grain grows where none was sown. Some of the gods survive or return, Vidar and Vali, Thor's sons Modi and Magni carrying their father's hammer, and Baldr and Hod come back from the dead. Two human beings, Lif and Lifthrasir, have sheltered in a wood and repopulate the world.
The renewal is the disputed element. Voluspa survives in two manuscripts with significant differences, and scholars have long debated how much of the renewed world reflects Christian influence on a poem composed or recorded around the period of Iceland's conversion, the returning Baldr, and the arrival of a "powerful one from above" in one manuscript, being the passages most often cited. Some hold the renewal to be a genuine pre-Christian element with parallels elsewhere in Indo-European material; others regard it as Christian colouring on an older and bleaker story. There is no consensus, and the problem is a standing example of the difficulty of reading pre-Christian material that survives only through post-conversion hands.