Moonfall

Moonfall is an event that is been the instigator toward the recent Dark Age in the world's history. This event is theorized to have occurred roughly 10,000 years ago (though some scholars suggest as early as 2,000). Many believe that the world once had a second moon, but for some reason the celestial body exploded and nearly destroyed the world in which it orbited. While there is some historical evidence that a second moon may have existed it is still a hotly debated topic among scholars.
What is known is that the world was once showered with a massive amount of debris from a natural disaster that occured beyond the boundary of the sky. Massive slabs of rock tumbled down along with smaller meteroite-like impacts. A dust cloud rose up over the world to shroud all in darkness.
The unnamed, advanced magitek empire which ruled the world at the time was all but wiped out entirely. There are theories and some archaeological evidence that these ancient peoples worked to stem the tide of destruction as best they could, bringing the full weight of their magical and technological might in order to prevent a total extinction of all peoples upon the world. Whatever they were able to do, however, it was not enough to save the empire that they had formed and all records of these people was buried beneath a wave of dust, rock, and earth. Most relics are only found deep underground in the modern era.
It is also believed that the Primal dragon gods arose from their slumber and shielded many sections of the world with their great wings before eventually going back into slumber once the worst was over. This would explain why areas around natural monuments that are attributed to these primordial beings went relatively unscathed compared to areas further afield.
The dark age that followed the Moonfall was long and forced many to rebuild from the basics while also allowing new species to rise up and claim a foothold within the world.