Ymir the primeval beeing, killed by Odin, Vili, and Vé, who created the 9 worlds out of his corpse. http://en.wikipedia.org/wiki/Ymir
This is a depiction of the great World serpent of Norse mythology that appears in a myth of Thor. Thor went to the sea-giant Hymir disguised as a youth and asked to go fishing. He then baited his hook with the head of a large ox and hooked the World serpent and attempted to pull it up. Hymir cut the line during the struggle and stopped Thor from killing it.