Fenrir, the monstrous wolf embodies strength, ferocity, destiny, and inevitability. Fearing Fenrir’s strength and knowing that only evil could be expected of him, the gods bound him with a magical chain to hold the beast in place for all time.
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 battle which will also involve the einherjar (the fallen warriors of Valhalla), a battle 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.