Seoul Station’s Necromancer - Chapter 1 Finally Seoul!.

Kael Veyne was betrayed, hunted, and left for dead in the depths of the Abyssal Dungeon.As an infamous assassin, he was the empire’s deadliest shadow—until the day his guild turned on him.Ambushed in the Abyssal Dungeon, his body was torn apart, and his soul was consumed by the abyss. But death was not the end.He reincarnates 25,000 years later with the Devouring Bloodline System. Kael awakens in the body of a noble scion sharing a similar name to him, and his very essence fused with eldritch power.With every kill, he absorbs primal energy, evolving into something far beyond human. Monsters, mages, mancers, knights, assassins—nothing is beyond his reach.

Chi Yan had always had a weak constitution, and ghosts had always tried to kill him. He had tried many ways to change his situation, but it was all futile.

Coincidentally, Third Master Ye of Shiming City passed away, and a priest informed Chi Yan that Third Master Ye possessed the “look of demon,” Carrying a bit of this man’s ashes and installing an altar for him at home could help control the evil spirits around Chi Yan.

Left with no choice, Chi Yan took a gamble. Amazingly, it worked. However he didn’t expect that he’d be instead be haunted by the most persistent ghost of them all.

Obsessed with love, undying resentment, possessed by evil.

- Description from Novelupdates

Transmigrating to the disciples of the Demon Sect, and relying on the skill modifier to become a giant of the Demon Dao.

[Detected the technique “Blood Nerve”, relying on devouring blood to practice]

[Side effects: easily affected by the spirit contained in the blood, becoming bloodthirsty, bloodthirsty, mad, and even brain dead]

[Please wait a moment, the system is being modified…]

[Ding! The modification is complete, and the side effects are cancelled]

- Description from novelbuddy

To pass as an imperial concubine, one must be professional.

Actually, the profession of an imperial concubine is pretty good. The emperor will accompany you in eating and drinking, and even pay you for it. What’s not good about that?