A little lesson in Northern Mythology: Fenrir was a son of god of fire Loki and Hrimthur (a giant tribe) Angrboda. Incest was a common good in those days, because the dude looked nothing like a human or giant, but like a humongous wolf instead. He was bad-tempered and ill-willed and so the gods thought up a plan to tie him up. After wolfman broke a couple of conventional chains they tried it with a dwarf chain. The chain was called Gleipnir and was made of six ingredients of varying questionable existence: the breath of a fish, the beard of a woman, saliva of a bird, roots of a mountain, the sound of a cat’s paws and tendons of a bear. Týr, the god of war, lost his right hand during the event as Fenrir bit it off.
There are more details to this story, but you’ll have to dig through Wikipedia for those yourself. They key message here is that Fenrir got pissed. And apparently he still is, because he’s still in chains. Must be looking for revenge. Long story short: cool title for a Death Metal song, an EP and a band: Wrath of Fenrir, all released last month.