Great Rain of Fire
The Great Rain of Fire is an apocalyptic event from the Mystara setting of Dungeons & Dragons. Specifically, it refers to when the advanced civilization of Blackmoor blew itself up in an enormous nuclear inferno, exploding so hard that it literally shifted the axis of the entire planet, combining a nuclear winter with an ice age all in one. Yeah, that's right, they nuked themselves so hard they shifted themselves partially out of orbit. That's either fail or so stupid it's awesome.
Needless to say, this fucked things up for pretty much everybody, and directly led to the reshaping of Mystara into the world it is today. The Kogolor and Shadow Elves are directly connected to the fallout of this cataclysm (no pun intended) and... well, let's just say that it was a good thing that Ka the Preserver had set up the Hollow World as a nature preserve.