In Taoist legend, the world went through three eras.
The first was the Ancient Desolate Era, when the heavens and earth were newly formed, and the world was chaotic and disordered.
Heaven and earth were a whole, within the same universe.
Various physically mighty members of the Witch Tribe and the Demon Clan roamed the world, undeterred even by Saints.
Later, a war between the witches and demons shattered the skies and cracked the earth.
The Witch Tribe's Gonggong broke Mount Buzhou, completely separating heaven and earth into two universes, marking the end of the first era.
The second era was the Ancient Era, when the Human Race rose, and the descendants of the Witch Tribe, the Demon Race, roamed the world, contesting aura with the humans.
Later, Emperor Yan and Chi You fought, turning the expanse of the netherworld's mainland into multiple universes, thereby ending the second era.