Born of the most bizarre origins, with bloodlines dating back to a time before the Sundering in some cases but only truly realized within the last thousand years.
When the Circle of Vecna managed to tear a whole between worlds, unspeakable entities were unleashed into this world. The resulting surge awakened daemonic bloodlines, possessed nearby humanoids, and perverted the pacts of warlocks. This massive transmorgification produced a susatinable population of these diabolic spawn.
Outcast from society at large, they banded together in Alienages and wilderness tribes.
A sizable Tiefling population has established itself in Vodarre, most notably the Baronies of Averos.