Douluo: Black Emperor

Nidhogg, the master of the earth's mythical period and the ancestor of the dragons, the Black Dragon King, was forced to death on the throne by the four monarchs leading humans and other races during the second dragon rebellion. His soul existed on the earth for tens of thousands of years, until one day it merged into a human body. Due to the power of the soul, it accidentally broke through space and came to the Douluo Continent during the reign of the Dragon God. At the time of the war between the gods, the Black King's fused human body was knocked down from the divine world and fell asleep on the Douluo Continent. Nearly a million years later, that life is reborn on this land again, and will cause a bloody storm between the two worlds... When I return, the world will also come to an end. ——Nidhogg