Ragnarök will be preceded by the Fimbulvetr or "Monstrous Winter", a period of three years of perpetual winter with no summer between. Snow will fall from all directions with great frosts and biting wind, and the sun will lend no warmth to the earth. During this time great battles will be fought throughout the world, humanity will descend further into violence and depravity, laws of kinship will be broken, and fathers, sons and brothers will rise up against one another. According to Völuspá, it will be an "axe age, a sword age, shields are cleft asunder, a storm age, a wolf age, before the world plunges headlong."
The wolves Sköll and Hati will then finally devour Sól (the Sun) and her brother Máni (the Moon) respectively after a perpetual chase, and the stars will burn out and vanish from the sky, plunging the earth into darkness.[6]
At that point Garmr, the monstrous hound that is bound at the cave of Gnipahellir, will begin to bay loudly. In response, three cockerels will begin crowing: Fjalar in Jotunheim from the forest of Gallows-wood, Gullinkambi in Valhalla who will wake the einherjar, and a third one that is not named, crowing in Hel and waking the dead.[7] The giant Hraesvelgr will sit on the edge of the heavens in eagle form and shriek with anticipation.
The earth will begin to tremble so violently that trees will be uprooted and mountains will fall, and all bonds and fetters will snap and break. Loki, god of mischief and strife, will be freed along with his ferocious son, the wolf Fenrir whose slavering mouth will gape wide open with his upper jaw against the sky and his lower one against the earth, but it would gape even wider if there was room. Flames will burn from the wolf's eyes and leap from his nostrils. Likewise, Garmr's "rope will break and the ravener run free". Meanwhile, Eggthér, a herdsman among the giants, will sit on a mound and joyfully play his harp in grim celebration of the coming holocaust.
At the same time, the oceans will surge up, drowning the land in a great flood as Jörmungandr, the Midgard Serpent, twisting and writhing in fury, makes his way onto the shore. He will proceed alongside his brother Fenrir, spewing venom and spattering the sky and earth with his poison.
Then it will happen that in the upsurge of waters, the great ship Naglfar, the ship of the giants (which is made from the nails of the dead), will be released from its moorings in Jotunheim. Set free by the catastrophic flooding and tsunamis caused by the Serpent, it will be carried along from the east, captained by the giant Hrym and transporting the legions of Jotnar toward the battlefield of Vigrid (Óskópnir).
From the north will sail Loki in a ship carrying a great army of evil people called "Heljar sinnar" (according to Gylfaginning which is not to be confused with people from Hel) to fight against the einherjar.[citation needed]
Amid this turmoil, the sky will open and from it will ride the fire giants of Muspelheim (the "sons of Muspell"), led by Surtr who brandishes a flaming sword ("burning with the sun of the war gods" according to Völuspá). They will advance from the south with fire before and behind them, tearing the sky apart as they too close in on Vigrid. As Surtr and the others ride over Bifröst, the rainbow bridge will break behind them and fall to the earth, while the mountains themselves crack open, releasing hordes of troll-wives upon the land.
All the forces of the Jotnar will thus arrive on three fronts to storm Asgard and will gather in battle formation upon Vigrid. They will all but fill that plain that stretches one hundred leagues in every direction.