The Twelve Apocalypses: A Damned Soul's Path to the Abyss - Chapter 13: Demonic Culture

I found myself possessing the body of a young master who everyone was eager to kill. I’m invincible, so let them try to kill me. It’s only for one second, though.

Ye Song, who once lived in a technologically-advanced world, died and reincarnated into a noble teenager’s body in another world.

A fantasy world filled with magic!

A series of events filled with tragedy, action, etc. began to unfold one after the other when he fatefully encountered one of the most guarded secrets of this world, obtaining the legendary power of Wizards.

Watch how he reaches unreachable heights as a powerful Wizard in this new world.

- Description from Novelupdates

Zavier met Cosmic Consciousness after his death. He was satisfied with every system that Cosmic Consciousness exhibited, so he wanted all of them. Surprisingly, the Cosmic Consciousness obliged him.

Zavier was reborn in an isekai full of magic and alchemy. Now, he had many routes to upgrade. Interestingly, to coordinate these systems, Cosmic Consciousness gave him the gift of being able to duplicate himself. He could clone a finite number of himself to manipulate these systems.

Magus, Alchemist, Mesmer, Tamer, Hunter, Vampire, Werewolf, Dragonknight, Necromancer.....

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By the way, it wouldn't appear NTR or some bullshit harem of courtships. MC of course will have harem but not for cliches.