Fenrir

Fenrisúlfr
Fenrir is a monstrous wolf, and the son of the trickster god Loki and the giantess Angrboda. Due to the gods' knowledge of prophecies foretelling great trouble from Fenrir and his siblings, World Serpent (Jormungandr) and Hel, the gods imprisoned him, and in the process Fenrir bit off the right hand of the god Tyr. He is fated to slay the god Odin during the events of Ragnarök, but then be slain by Odin's son, Vidarr.
Myths and Legends
Chaining

He is forever growing and most chains cannot hold him. He was invited to Asgard and was chained there multiple times, but broke them off with a simple shake. In the end, the gods went to the dwarves for their help. They made a rope called Gleipnir, containing the roots of a mountain, the breath of a fish, the sound of a cat's footfall, the sinews of a bear, the beard of a woman and the spittle of a bird, all of which were impossible items to obtain.
This weak-looking rope was offered to Fenrir and, suspecting it to be a trick, he asked for a god to place his arm in the wolf's mouth. The God of Courage, Tyr, volunteered. When Fenrir was bound, he couldn't shake off the chain and bit off Tyr's hand in revenge. He will remain bound until Ragnarök, the doom of the gods. Fenrir himself will battle Odin and devour him. Odin's son Vidarr will avenge his father by ripping apart the wolf's jaws.
Fenrir and Ragnarok


Ragnarök will begin with a series of highly destructive earthquakes. This will also crack the boulder Fenrir is anchored to, hence, freeing him from the bonds of Gleipnir.
Maddened even more due to years of captivity, Fenrir will then rampage through The Nine Worlds, devouring anything and everything that comes in his path. Hati and Skoll, his two children of a similar form, comparatively smaller in size, will accompany him.
Together, they will destroy the sun and the moon that will send the Norse universe in utter darkness and create a chaotic mess.
It was believed that Fenrir would break free from his imprisonment and fight side by side with giants against the gods on the day of Ragnarök. He would then sweep and devour everything including Odin with his lower jaw buried in the ground and his upper jaw up in the air. Odin’s son Vidarr would avenge his father by killing the giant wolf.
Vidarr is believed to possess enough strength to rip apart Fenrir’s jaws, finally killing the Giant Wolf.