Bennu is a phoenix bird that lives in the deepest part of the underworld. Every breath and every breath is the fire of hell. According to legend, Pluto Osiris is one of the incarnations of Bennu. The Bennu bird possesses the magical power that all demons dream of, and has no interest in power or killing. Despite this, it still enjoys a great reputation in the world of humans and demons. In order to become the overlord of the underworld, many lords divided the territory of hell. For thousands of years, they have been killing each other, but no one dared to touch the habitat of the Bennu bird. During the heyday of Plague King Abaddon, he led an army of locusts to Acheron on the River Styx, occupying most of the Demon Realm. Even Beelzebub, the Ghost King, was driven to the other side of hell. However, once the army arrived at the habitat of the Bennu bird, they did not dare to step beyond the Thunder Pond. Bennu is the nemesis of all demons, the natural enemy of Abaddon, and the God of the Underworld.