Seoul Station’s Necromancer - Chapter 138 - Lord of Pestilence

Carn wakes up from a vivid dream where he spent a thousand years as a gargoyle, guarding a demon lord's tomb.In this dream, he possessed supernatural powers, including the ability to teleport and instantly kill anyone within range who broke eye contact with him. Heroes, saintesses, adventurers, all fell before him.When he returns to his normal life, things take a strange turn. Carn realizes he still has the gargoyle’s powers, and the world he has woken up to seems different.But adjusting to the new reality is not the real issue. Carn brings back something nobody in this world has imagined. Not only he imports his powers to this alternate Earth, but he also carries over his gargoyle instinct and his hobby. He loves snapping human necks.Whether it's ordinary humans, explorers, super soldiers, cyborgs, mutated beasts, monsters, or mysterious entities from other dimensions, Carn eagerly anticipates snapping their necks, one neck at a time...In secret, of course.

When other people experience a body transformation, it is inevitably either male to female or female to male.

Me? I wake up to find myself transformed into two different bodies.

Both a male body and a female body, one conscience operating two bodies, all sorts of embarrassing moments.

Walking together normally makes other people think that I am sweethearts with my other-self, such sadness.

Also, the entire business of a hero rescuing the beautiful maiden, I call Bull.

I get slashed by a sword and my female body gets abducted, and he wants me to thank him?!?! Can it be less of a tragedy?

- Description from Novelupdates

Though he received the skills necessary to teleport across worlds, the king who performed the summoning ritual attempted to trick him into wearing a slavery collar, this annoyed him so he kidnapped the princess and returned to Earth.

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!