Might be running a #burningwheel game soon, and I'm thinking of shamelessly ripping off Arx Fatalis and NK Jemisin's #brokenearth novels. My quandary is which of these is most exciting:
1) The immediate aftermath of the cataclysm as a group moves into a vault/shelter
2) The internal dynamics of a community while the cataclysm still rages outside, no end in sight
3) The fate of a group as the calamity begins to subside and leaving the "vault" becomes viable
@auguryignored depends on your group, 3 is probably the most open, 2 is the plot of Paranoia, but if they are not combat bunnies perhaps option 0, where you know the cataclysm is coming and the planning to survive...
Neal Stevensons Seveneves covers this well in a sci fi setting.