Black Fire War
Long ago, a human kingdom lay to the southeast of Summerlund, across the Bright Sea. This kingdom, called Falwyth, lived in harmony with the neighboring Empire of Azmartheon, ruled by the dragonborn. The dragonborn taught many secrets most ancient to the humans of Falwyth, and the humans aided the dragonborn, who were powerful but not numerous, in their various constructions and work.
Over time, however, the nobility of Falwyth became slowly dissatisfied with this arrangement. The dragonborn had longevity that they did not possess, as well as an inherent power they could not share. The nobles of Falwyth began to imagine that the dragonborn were slowly positioning themselves as lords over the humans, and they began to crave a greater power still. In their thirst for more power and knowledge, the nobles of Falwyth began to ally with devils in exchange for what they wanted. The dragonborn, largely in service of the goodly god Bahamut, begged their human allies to break off from this course, but this merely made the nobles think they were on the right track. They performed dark deeds in secret to please their new infernal allies.
Finally, the humans were offered a ritual that would forever bind them as rulers of the lands of Falwyth. They agreed, and the sacrifices they made to the devils were most unspeakable. When they emerged from the cave where the ritual had been performed, they had been wholly changed. Devillish horns and tails marked them and all their descendants as a new race, the tieflings. Worse, the ritual had allowed many fiends to emerge from Hell, ready to do battle with any who challenged Falwyth’s rule.
The dragonborn reviled this change in their neighbors and went to war to try and stop this madness in their former friends. The war, fought between dragonkind and fiends, was a terrible thing, lasting over a century. It was only ended by the terrible destruction called The Rending, which utterly shattered the lands. Azmartheon became a blasted desert, while Falwyth became a broken archipelago of worthless islands, each lorded over by a tiefling despot.
Happily, this terrible war was not the sum total of the Falwyth legacy. Peaceful Falwyth humans, along with some of the younger tiefling nobility who were horrified by their parents’ actions, departed Falwyth, heading across the sea to Aldorath. They landed on the eastern coast and formed the new Kingdom of Summerlund. The tieflings, fearing their corruption their blood symbolized, abdicated rule in favor of new human rulers.