The Great Calamity

The Great Calamity was an event that happened after the Nephilim had freed Tharizdun. The world before this was a collection of floating islands, hotter the lower it was or colder if high up. But in his rampage the many islands where clashed together forming crude continents. In the fallout after the gods had rid themselves of Tharizdun for the time being they set to rebuilding the world so it could be populated with races less prone to self destruction. The nature gods pieced the puzzle together and provided resources that otherwise were in short demand. Lolth and the dwarven gods carved out the caves and underdark although Lolth soon was exiled.

In this process the Nephilim's were left behind in the new world as ruins in out of the way locations.