At the edge of our world, there are two vast worlds built by magic, the Dark World under the rule of the Demon King and the Light World guarded by their patron saints. According to legend, it was their collision that gave birth to the buffer zone in the middle where magic can be taken undefended - the human world.
At the beginning, when darkness and light faced off, everything was chaotic and unclear. The Demon King of the Dark Realm was slightly better. At the last moment, he eliminated Mingying, the patron saint of the Light Realm, and separated the two realms.
Although the Demon King won the battle with Mingying, his powerful soul was sealed in a deep sea black pearl by Mingying and could not move for many years.
Then, an unknown number of years passed. With his nostalgia for the Dark World and the call from the Dark Pond, the darkest one in the Dark World that gave birth to him, part of his soul gradually took shape in the Demon Realm, regained his authority, and carried out several glorious integrations of the Demon Realm. Finally, the prosperity of the Demon Realm grew with his soul. Like the sun. His reputation spread far and wide. Needless to say, the people of the demon world, even if they hear about it from the distant light world, they are always frightened and work hard to seek their own development and growth in order to escape the threat of their old enemy.
Like Achilles' ankle, the terrifying Demon King also has a weakness: his soul is incomplete. This also made him forever imprisoned in the Demon Realm, near the Black Pool. Unless he can find the black pearl that seals his soul and crush it by an external force completely different from the power of darkness.