Nightfall is the name given to the event of the Perishing Star striking Earth, colloquially referred to as the Apocalypse. As a result of this event, the city of Maria was destroyed and the region that would become DisSea and DisCity transformed into a colossal death zone from which supernatural catastrophes ravaged the world. Although superficially normal society continued for some time, all man-made satellites were destroyed, the environment rapidly, deteriorated and human population plummeted as a result, plunging humanity into a new dark age where science and technology came to a halt. Conflict over dwindling resources led to nuclear war between surviving nations, thus further eradicating the old world's civilization.
Eventually, a series of conferences was held, which resulted in the Nightfall Proclamation in N.F. 141 abolishing the old world order and adopting the new Nightfall (N.F.) calendar, with the year of the meteor strike as N.F. 001. In the new era, old nations were dissolved and survivors around the world congregated around independent city-states. Survivors also signed the Nuclear Restriction Pact, banning all nuclear technology, including for energy production.