Forsaken Priest of the Hero's Party - Chapter 29: The Demon Kings Resolve

“Why don’t they think about training to grow stronger during a time when just breathing makes you stronger?”After possessing someone, he decided to silently train to become a great mage.“Did it appear?”[You have acquired the All-Attribute Body (Fire, Water, Wind, Earth, Wood, Electricity, Light, Darkness).][You have acquired the highest-grade elixir, Dragon’s Essence (SSS).]……Let’s take a slightly different path to growth from others.

In the current era, people are either normal or are with ‘special abilities’. Cases related to the latter are managed by the “National Anomaly Prevention and Control and Special Species Management Office”.
Qi Zheng Emperor Sheng Lingyuan was reawakened a thousand years later after he jumped off the fiery Red Lake. Xuan Ji, a newly transferred staff to the Reparations Division of the Deviant Control Office, finds himself having to clean up the mess of a revived tyrannical monarch. The two seemed to share something from the past, but unbeknownst to them, a big conspiracy is stirring right underneath their noses that could destroy the balance of the world.

- Description from Novelupdates

To save a doomed fantasy world, I killed the main characters, then destroyed the game world, and fell into another timeline as the academy's top seat and rival to the protagonist.Now, I'm trying to save the world and steer it towards a better ending…But I'm the final boss.

Seo Tae Hyuk, jailed after being falsely accused.