This category collects scenarios that are liable to conclude with the end of the world... at least as humans understand it. If the universe ends, the world is overrun with Mythos horrors, or the entire human race turned into sandalwood ornaments, the scenario probably belongs here.
The result doesn't have to be inevitable, but it should be reasonably short-term. If the world is utterly doomed, but not for another hundred years when the stars are right, it's not going to make much immediate difference. Similarly, if dooming the world is technically possible but practically implausible, the scenario probably doesn't need to be here.
Scenarios might go here if "the world" will end, even if remnants of humanity survive on other planets, sheltered enclaves or alternate realities. If a follow-on game would deserve the moniker "post-apocalyptic", consider that a hint.