500th Time Reborn, A World Only Known By Women: The Karma System - Chapter 23 So Good

Apocalypse befell, and roommates performed a skyward ritual.As the fog descended, the Book of Blood Spirit appeared in the hands of all survivors, and only those with a Contract monster could survive.Su Han directed his gaze to the neighbor who had already mutated and twisted, silently pulling out a gleaming fruit knife...Grotesque meat corpses, giant spiders with gaping mouths, eyeballs enveloping the city, one-eyed sharp-toothed hand monsters...Civilization fell, cities shattered, and all humans became meat for the monsters. There was only one way to survive:Use monsters to fight monsters.

It was in the year 2800 of the Midgard calendar. Back then, there was a Overlord who once reigned supreme and had reached the very brink of subduing the world.