Humanity vanished when an unholy tyrant with his minions of cursed NC attacked Sacred Naphis had died by sacrificing her will and soul to take the tyrant with her to death sunny didn’t give up he searched for a solution to rewrite fate itself and he found copying nightmare spell he sends his soul back in time to his 16 years old Body
This is honestly one of the best fanfictions of shadow slave that I've read, you should post it on ao3 for more views