I Sought Immortality, Yet Ultimately Became the Demon Lord

A cultivation novel with no formulaic tropes, a genius protagonist, decisive and ruthless action, and a passionate female lead. No male lead. (Includes a woman disguising herself as a man.) It leans dark. Qi Refining and Foundation Establishment, Nascent Soul and Deity Transformation, Tribulation Transcendence and ascension. The road to cultivation stretches on without end. Ten thousand years pass in the blink of an eye. Looking back, the past is like smoke drifting before one's eyes. Since the divide between heaven and earth, immortals have vanished from the world. Rising from humble beginnings as a mortal, the greatest martial arts genius sets foot on the road to immortality, seeking the immortal path for one reason alone: eternal life.