Voted Frontier/Discovery, but could as easily have been Downslide.
In current campaigns I'm participating, there are a lot of apocalypse / post-apocalyptic settings. In one game, the city we're in suffered a terrible earthquake (probably caused by us), in another, the whole land was transformed when demons invaded it (there's a big cloud covering hundreds of square kilometers), in another, we caused the Plague (but things seem to be ok now) and lastly, in my game that hasn't started yet, the Sun God was captured / put in a "coma" by the collective efforts of the Goddess of Night and the God of Dreams.
TS.