For ten thousand years, the mortal realm lived in relative peace and prosperity. In the Celestial realm, the gods sheltered themselves, and lived in harmony, believing themselves safe. In the Infernal realm, the six Lords of Hell fought amongst themselves and tortured the unfortunate souls who found their way to that dismal domain. Thus, both the Celestial and Infernal realms left the mortal realm alone.
In the mortal realm. nations rose and fell. The people built villages, towns, and cities. Over time, other people sacked and burned these settlements, and built new ones in their place. The people migrated and formed new civilizations as they abandoned the old ones. The people fought wars amongst themselves and signed peace treaties when they could no longer stomach war. Time marched ever forward, and the people forgot the lessons of the past.
Peace could not last forever. In another universe, Exterminis, alone in his prison, forgotten by gods and mortals alike, began to stir.