Ragnorok

The end of the cosmos.
The Twilight of the Gods. The time of fire and ice.
The great battle at the end of time between the gods and the Frost Giants in which the world will be destroyed and made anew. Ragnarok will be preceded by three winters of bitter wars followed by the Fimbulvetr, a winter so cold that the sun will give no heat. Then the forces of evil will gather and make war on the gods.

First comes the signs, such as three years of winter.
The wolf, Skoll will devour the sun while the wolf Hati will eat the moon.
The stars will vanish from the sky and Fenrir will break free.
The battle that the slain warriors have prepared for will begin.
Most of the Gods will perish.
All nine worlds will burn and the earth will sink into the sea.
After, a new world will be born with the Gods and man living together without wickedness.

Sources: Varrious

Norse/Teutonic Gods and Goddess
God and Goddess Index