Tieflings are the descendants of a human empire, which the stories say was called Bael Turath, which made a terrible pact for power with a powerful Devil, tainting their entire population with overtly fiendish traits. Though their personalities are as varied as any other race, they tend towards arrogance and fiery tempers, though whether because this is in their nature or because they have grown tired of defying others’ expectations, none can say.
Tieflings have proportions and basic physiology much the same as humans, but with several important differences. Most obviously, Tieflings have horns and tails. The horns vary considerably among individuals but are rarely sturdy enough to use as weapons, while the tails, though thick and powerful, lack the precision to be used as an appendage. Most Tieflings also have fangs, and eyes without pupils that most commonly are black or red. Their skin ranges from red to purple to blue. There are tales of Tieflings from specific bloodlines who exhibit other physical changes
Aside from their physical differences from their human ancestors, Tieflings also have innate magical powers derived from their unholy origins. Flames and heat do not harm them as much as others, and all Tieflings exhibit the ability to manifest minor frightening effects such as making their voices boom, causing doors and windows to slam, or a minor tremor to pass through the earth. While these effects are not dangerous, they are proof if any were needed of the otherworldly source of a Tiefling’s power, and most humans and other mortals find them very unsettling. Tieflings of particularly strong will also manifest the power to burn those who dare to attack them with flames from hell and to shroud themselves in unnatural darkness.
Language and culture
Tieflings have passed down knowledge of the Infernal language spoken by devils. Their version of the language has softened over time, but Tieflings and devils still understand each other. There was once a specific accent with which Tieflings spoke the Common Tongue, but centuries of diaspora and mingling with other human cultures have all but stamped it out.
The destruction of their empire has left Tieflings with little culture to call their own. Many surviving families have specifically rejected any remnants of their past, seeing it as cursed, while others have simply lost touch with the old stories and traditions, instead adopting those of their new, mostly human homes. Tieflings do tend to stick up for one another, though, and the constant suspicion levelled at them by other folk lead them to exhibit great loyalty when individuals or communities show them trust.