Am I Mentally Ill? There's Just a Black Dragon in My Head

[Ruthless and decisive! Dark and evil! Devouring and evolving! No saintly heroine nonsense!] Everyone says mental illness means having a split personality, but only Gu Qiye knows that it’s the most authentic version of himself. Thirteen years ago, he broke all his own fingers and evolved black dragon claws. Eleven years ago, he pulled out his two canine teeth and evolved dragon fangs. Ten years ago, he chopped off two people’s heads because they had both been possessed by false gods. Eight years ago, he fell and split his head open, causing dragon horns to grow. Six years ago, his body was burned, causing dragon scales to grow. Four years ago, he was stabbed blind, causing the eyes of a black dragon to grow. Two years ago, he gained the black dragon’s power for the first time and killed a false god who had possessed a human. Later, countless false gods from another dimension descended, seeking to replace humanity, the race chosen by fate.