When a person dies, his soul is divided into three parts. The heavenly soul returns to heaven, the human soul stays in the grave, and the earthly soul returns to the earth. There is the earthly realm in the east and the underworld in the west, which accommodate the earthly souls of the world. The black and white warriors are permanently appointed in the east earthly realm to guide the earthly souls into the underworld and follow the great way of heaven and earth to protect the principles of nature.