the flame war
The flame war was between the human kingdom of Tiefos and the dragonborn city states of Wyrmhold. Lord Byros of Tiefos had claimed the land Wyrmhold was founded upon at the end of The Seed War but the Dragonborn refused to honour this claim. In order to overcome the Dragonborn Tiefos entered into an infernal bargain, transforming the humans into Tieflings, however, even with their new found power, they were still unable to entirely defeat Wyrmhold. The war left both nations so weakened that after a succession of barbarian raids they were unable to stop an orc horde that had formed. Both kingdoms were destroyed and the remaining populations dissolved into the human kingdoms of the area. The land that used to make up Tiefos and Wyrmhold became The Burnt Wastes.