From Saint to Demon Lord

Chuyi was born with demon bones, which under sect law is a sentence rather than a condition. Her brother Xie Wuwang, the sword sect's finest, went looking for something that would let her live. While he was away the sect's goddess Lin Wan cut the demon bones out of the girl and killed her with lightning. He came back to a soul lamp already going out. His hair turned white, he went over to the demon path, he put the sect that raised him to the sword, and then he spent a hundred years walking the world looking for a sister who was supposed to be dead. She has been reborn as Jiuyou, saintess of the demon clan, with none of it remembered. The people around her feed her a version of the past in which her brother is the man who murdered her, and she believes it enough to drive a poisoned blade into him. He does not stop her, because taking the wound is the only way she will see the rest. The truth surfaces while he is dying, and she is left holding her own origin blood and a decision about what to spend it on.