A man in the Tianyun Cultivation Realm, reborn with memories from three hundred years in the future.
[You have been reborn. There are 9,527 days until your master, Luo Wuchen, seizes your body. That will be the most miserable moment of your life. Now that you have returned, you swear to make Master Luo Wuchen pay the most excruciating price.
Mission One: Refine your master, Luo Wuchen, into a Blood Fiend Corpse. Reward: Corpse King Reincarnation Art, which lets you split your soul and enter a blood corpse to live another life!]
What? Turn my master into a corpse? How could I do something so outrageously immoral!
But then again…
Years later, Lin Ye sat atop a corpse-suppressing coffin, holding the Banner of Ten Thousand Souls. Behind him lay a mountain of corpses and a sea of blood, while demonic qi surged into the sky. Countless corpse-ridden zombies and green-faced, fanged wraiths lurked in the billowing black smoke. He sought to attain the Dao through demonic cultivation and ascend to immortality.
Only then did the many cultivators of the Tianyun Cultivation Realm realize that Lin Ye, who appeared to be a righteous powerhouse, was actually a demonic corpse-refining overlord guilty of countless atrocities.
“Old Demon Lin Ye, the evidence is conclusive! How can you still claim you’re not a demonic cultivator?!”
“Fellow Daoist, don’t talk nonsense. Please, take a seat in my banner!”
It's from the harem story, right?