Bog Standard Isekai - Chapter 39Book 3. .5

Sometime after ‘Gates’ appeared in this world, humanity was divided into two: [User] and [ordinary human beings] Lee-kyung was able to awaken into a user and choose a [Class]…but, in momentary misjudgement, chose to be a [Necromancer], the worst of all classes.

Lee-kyung, searching for the materials to evolve his skeletal servant, ‘Lackey,’ was barely able to participate in a high-level raid for [Tower of Command] Dungeon. In an accident, he falls down alone to uncover a hidden conspiracy.

Injured and desperate to survive, Lee-kyung called out to anyone…and reached a vengeful spirit. “Please, I’ll do anything….Please form a contract with me and save me!”

–-You’ll do anything?….

TW: Depictions of mental health

Chen Rui, an otaku from earth, is reborn into a human body in another world, who falls into the legendary evil, brutal world of the devil called Mozu where humans are treated as food. He has to survive while facing horrors of the devil, violent dragons and a variety of power enemies depending on a strange super system chip and his wits. Surrounded by Devil’s beauties such as black-bellied lolita princess, cold queens, violent dragons, charming poisonous devils …

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!

- Description from Novelupdates