Xianxia: Why am I here? - Chapter 120

He is a young man without a spirit root. It is believed that this denies him the chance at cultivation. However, a mysterious lady imparts a Supreme Demon Classic to him and from then on, he starts his path of cultivation.
He undergoes a total transformation to emerge as the most fearsome and powerful fiendish demon in his era, that even immortals and fiends are fearful of him, and saints are at his beck and call.
Mastering the Supreme Demon Classic is the turning point in his life. He is able to unleash his immense and divine power from within, illuminating the entire universe!

- Description from Novelupdates

On her wedding day, she was humiliated; her status as the legitimate wife was instantly changed into that of a concubine.

Taking place within a world of Measurements―superpowers owned from birth, with most being absolute trash.A world involving numerous secret organisations looking to take advantage of those rare and remarkable few possessing exceptional powers.When there exists Forbidden Knowledge better left unknown.When the discovery of said knowledge results in the inevitable; a world-ending catastrophe.‘Ignorance is bliss.’Fighting against the unrelenting persistence of the one who knows all.Before the tragic fate of the world repeats itself once more.―He must be stopped.

With divine medical skills in his left hand and supreme martial arts in his right, carrying a century of memories, he was reborn and returned to the city. This life, he vowed to dominate everything, take control of all, and ascend to the zenith of the heavens!