Chaos grips the Tang Dynasty as the An Lushan Rebellion tears through the empire, and monsters roam the Central Plains while the people suffer in poverty. Li Haobai sets out from Bashu, hoping to reach the front lines and earn merit through great deeds. Along the way, a monster swallows him. By chance, he fuses with the guardian of the dragon's veins and gains the power of the black dragon. From then on, he is caught up in the struggles between rival forces in this action fantasy adventure.