Ragnarok

The wolves chasing the Sun and Moon will catch and eat them, and there will be bitter cold. The earth will shake and mountains will fall, and even Yggrasill, the World Tree will tremble. Heimdall will blow his horn one last time.

Now all monsters break loose. The wolf Fenrir will swallow Odin, but will be killed by Odin's son, Vadir. Thor attacks the World Serpent and kills it, but is poisoned by its venom. Loki will break free and attack Heimdall, the keeper of Bifrost the rainbow bridge, which gets shattered.

All the gods, monsters and giants will die, and the world will be burned, and then swallowed by the ocean. However, a new, better world will arise from the waves, lit by a new sun.

Ragnarok and the wolf Fenrir are in the book "The Weirdstone Of Brisingamen" by Alan Garner.