Fenrir, the monstrous wolf embodies strength, ferocity, destiny, and inevitability. The reason why Fenrir was greatly feared amongst the gods was that he is prophesized to kill the chief god of gods - Odin the Allfather at Ragnarok.
It was foretold however that at Ragnarok, he will break free of his chains and run throughout the world with his lower jaw against the ground and his upper jaw in the sky, devouring everything in his path. Most importantly he will go into battle with the Allfather Odin in an epic skirmish which will also involve the einherjar (the fallen warriors of Valhalla), a fight that Fenrir would be victorious in. Enraged by the death of his father, Odin's son Víðarr, charged Fenrir to avenge Odin.
Vidar managed to kick and hold open the monster’s mouth and stab his sword through the wolf’s throat, killing Fenrir and ending the destruction.
