Map of the Tiefling Empire of time
by Mike PhillipsQuick and dirty animation showing the Tiefling empire over time (from James Mishler's timeline):
Orange == Beastmen invasion, Purple == Tieflings (purple-striped == civil war), Red == Dragonborn, Cyan(ish) == Nithians
The timeline was not specific on the Dragonborn empire's founding, and I didn't distinguish between the two incarnations of Bael Turath. I arbitrarily pulled them out of Glantri in the collapse. Oh, and I haven't incorporated the canon timeline.
I just wanted to get a handle on where they covered, for purposes of sprinkling ancient Tiefling ruins around in my game (since I'm adopting that timeline into my campaign's timeline).