Demons or monsters that devoured humans were common throughout the affluent Tang Dynasty, and powerful demons or monsters would even disguise themselves as humans to hide. Xiao Du and his friend Xiao Bai, who had been kidnapped as slaves, barely survived by assisting traffickers in keeping the demon/monster neidans alive. They were assaulted one day by a monstrous demon disguised as a human, and they were saved by the sword immortal Li Taibai.