Nidhogg

In Norse myth, Nidhogg ("tearer of corpses") is a monstrous serpent that gnaws perpetually at the deepest root of the World Tree Yggdrasil, threatening to destroy it. This serpent is always bickering with the eagle that houses in the top of the tree. It lies on Nastrond in Niflheim, were it also eats corpses to sustain itself. Nidhogg is not the only serpent whose task it is to destroy the World Tree. Other serpents include Graback, Grafvolluth, Goin and Moin.