The Founder of Diabolism

Xian: the state of immortality that all cultivators strive to achieve. However, there is a dark energy that lies underneath—the forbidden Mo Dao, or demonic path. Through an unfortunate series of tragedies, this is the path that cultivator Wei Wuxian experiments with during his teachings. His rise in power is accompanied by chaos and destruction, but his reign of terror comes to an abrupt end when the cultivation clans overpower him and he is killed by his closest ally. Thirteen years later, Wei Wuxian is reincarnated in the body of a lunatic and reunited with Lan Wangji, a former classmate of his. This marks the beginning of a supernatural mystery that plagues the clans and threatens to disrupt their everyday life. Source MyAnimeList