True Devil of the Apocalypse

The apocalypse came out of nowhere, with no indication. It just appeared. Nobody could even begin to think such a thing would happen, so everyone was caught off guard. It wasn't even a normal apocalypse like those seen in movies, rather it was one full of horrors straight out of a fantasy world. Demons, mutated undead, monsters and many more. All those appeared on Earth from nowhere. Still, everything wasn't too bad as humans were granted a System to assist them in survival. Here is the story of one unlucky person who died before everything even began and how he came back to destroy everything.