Eternal Spirits

Eternal Spirits are the rarest beings of Mirror Worlds. They belong to the humanoid species and to the sub-type of Mirror Beings. Eternal Spirits are the rulers of the Mirror Worlds and rule as a family, even though they usually come from different families.

Definition
To become an Eternal Spirit, you need to be born as a Spirit. Spirits are Mirror Beings who are the children of one Celestial Being and one Infernal Being, it doesn't matter which specific realm their parents are from. However, not all Spirits are strong enough to become an Eternal Spirit. They have to cultivate for a long time, until they are able to fully control and balance the bright and dark sides in themselves.