Before humans were created, this world was inhabited by demon spirits and wild animals. Because of the times, they began to evolve and began to understand how to cultivate.
Demon spirits continue to cultivate so that they can have bodies, just like animals. This is the origin of the creation of demons with physical forms. Once they have physiques, demons begin to destroy the world. They kill animals and destroy nature without thinking about the risks.
The Gods descended to the mortal realm to scorch the demons to prevent the demons from doing as they please. Unfortunately, not all demons could be eliminated. Therefore the Gods created an heirloom to seal the demons, and they only captured the ancestors of the demons who corrupted the earth and killed them. Demon spirits they encountered, because the number of demon spirits was out of control, some demon spirits were still able to escape from the pursuit of the gods.