He appeared thirteen times.
Only thirteen times, and from the first to the last, he was seen as the demon who brought about the apocalypse. He appeared only thirteen times, each time at least two million people died. He wore a mask, so no one saw his face. There was no clue who he was, except for his voice. And his voice was useless.
Each time he came as if from nothing, slaughtered, and then left. Not once was he defeated, not once was he seriously wounded. There was no one who could fight him alone. The only thing the strongest people on the field could do was to evacuate as many civilians as they could.
Wherever he set foot, the place was devastated as if a nuclear bomb had fallen.
Dungeons? Creatures? Those who used their skills to abuse the system? Terrorist organizations? Large-scale wars and the like?
None was as great a catastrophe for the world as he was. He was the true apocalypse of this world.