Ymir

Ymir is a primeval being born of primordial elemental poison and the ancestor of all Jotnar. Odin used fragments of the giant's heart to create Midgard. The fragments, known as Heart of Ymir, maintain Midgard's integrity and feed its growth.

Before there was anything in the world, there was Ymir and empty earth. He created sons and grew as a result. But his sons—Odin, Vili, and Ve—grew as well and in time they attacked and killed Ymir. When he fell, his blood flooded the world and killed everything in its path. Only Hvergelmir managed to escape the flood of blood and swore vengeance in what became Jotunheim.