Chronicles of Khaldun: Crux of Eternity
The Dawn War
In ancient times, before the great empires of men and demihumans, there was the Dawn War. A fight between the gods and primordials for reality itself, the Dawn War raged for years (or perhaps centuries; it is unclear how time passed in those days before history).
Whatever the case, it was a massive struggle between the forces of Law and Chaos. The primordials crafted creation, the gods shaped creation, but the primordials sought to return everything to the primal chaos from which it was built.
There are many tales told of those ancient days, but most scholars simply recall the war itself. Several gods, now long-forgotten, were destroyed in the fighting, but the war ended with the deities victorious. The primordials were either slain or locked away, and the mortal world was declared separate from the affairs of gods or primordials.