A Reincarnated Mage's Tower Dungeon Management - Volume 4, Chapter 10 – Tower of Death?

Crossing to One Piece world, he became Roger’s younger brother.

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.

To the one who has never owned, obtained, or enjoyed anything throughout their entire life.“You have been chosen.”Thus, I shall bestow this power on you, for you are ’empty.’The power of the Void.Be my apostle and carry out my will.

Gods and demons fought, the worlds collapsed, only eternal immortal realm, lasting in the world.

After eternity, a god of war named Zhao Yun condensed the heavens and the earth, recast the cosmos, from the blue to the earth, marked the eternal immortal realm, in the name of the god, the king is over the world.

Since then, what he said is a myth.

- Description from MTL