Villain's Return from Retirement

A scientist doodled with his console and caused the world to change permanently. Mana rains down—and humanity seeks refuge underground to evade animals that benefitted from mana more than humans did. People in power stated that, but it was nothing more than a lie. A lie that was soon exposed by criminals, and caused the world to be split into two. --- Viktor, once a notorious criminal, renounces his past for love, only to face tragedy. Bereft of his wife, he resolved to lead a virtuous life in honor of her memories—aspiring to reunite with her in the afterlife. But that didn't last long. Killed, he found himself thrown into the afterlife without being able to repent. In a desperate bid for redemption and revenge, Viktor strikes a pact with an entity there. Little did he know, his fate was fixed the moment the deal was made.