As far as it is known, Ymir has long been dead.
In Midgard, in the North, it is believed that Ymir’s skull is the sky, his flesh the earth, and his blood the sea. Though, these claims could merely be the boasting of proud Odin and his brothers, who take credit for slaying the first jotunn and fashioning the earth from his body parts.
At the beginning of time, the Realm of Fire, Muspell, and the Realm of Ice, Niflheim met at the place called Ginnungagap; the void of space. Steam rose and froze again, and from that primordial mixture, Ymir, King of the Frost Giants took shape. From his body dripped other beings that would become the ancestors of Gods, Men, Dwarves, and of course, Giants. Even the mighty Odin must claim Ymir as his grandfather. Yet Ymir, like all giants, was an evil creature and led his Giant brethren against the Gods. After ages of warfare, Odin and his brothers slew the Giant-King and forged the world from his remains.
Yet there are other whispers. Rumors that Ymir, though not a God, was still a Primeval Being, and as such cannot truly be destroyed. Perhaps he only lies dormant in Niflheim, the realm of ice, eager to return and wreak vengeance upon Odin in his kin.