Rebirth in the Gu Realm: I Almost Obtained the Demon Lord's True Inheritance

[Demonic cultivator + villain + no female lead + ruthless and decisive + Gu poison] In her previous life, Ning Hui had glimpsed the true teachings of the Demon Lord, and ultimately died with resentment. However, he did not perish; instead, he was reborn into the body of a severely injured and deceased boy who raised Gu poison. Now reborn, he is treacherous and ruthless, embarking on the path to immortality with the guise of a demon! Despite facing death nine times, their resolve remained unchanged; through hardships, their determination grew stronger. After hardship comes happiness; an undying demonic heart can shake the heavens!