During the Genesis, there was a giant named Ymir.

Ymir's corpse is the basis of the land we're standing on, and it's blood became the sea.

Its two eyes became the sun and moon. I'm sure you're familar with this story, no?

The heart that contained all of Ymir's power was shattered. The pieces scattered all around the world.

Sage Varmunt was fascinated by its powers and conducted countless experiments to create the "appropriated heart of Ymir".

It's power was strong enough to fly aircrafts, or even power incredible weapons like the 'Guardians'.