Tieflings

Humans with the blood of fiends, most tieflings in Faerûn share a common connection due to the machinations of the archdevil Asmodeus a century ago. Tieflings are known for their cunning and personal allure, which makes them excellent deceivers as well as inspiring leaders when prejudices are laid aside. The Mark of Asmodeus
During the Spellplague, Asmodeus consumed the divine spark of Azuth and thereby achieved godhood. Subsequently, Asmodeus and a coven of warlocks, the Toril Thirteen, performed a rite wherein the archdevil claimed all tieflings in the world as his own, cursing them to bear "the blood of Asmodeus." This act marked all tieflings as "descendants" of the Lord of the Nine Hells, regardless of their true heritage, and changed them into creatures that resembled their supposed progenitor. The other folk of Faerûn, unnerved by the appearance of these devil-beings, became suspicious of all tieflings and occasionally hostile to them.
In spite of what some people believe, however, Asmodeus exerts no power over his "children," and tieflings today are as free-willed - and willful - as they ever have been. Some do choose to serve the Lord of the Nine Hells and his schemes, while others align themselves with different fiendish factions, or none at all, doing their best to stay out of infernal politics.
Since the ritual that spread the curse of Asmodeus a century ago, tieflings have been born on Faerûn that belong to tother infernal bloodlines, but those that bear the mark of the archdevil (and their descendants) remain the most numerous examples of their kind by far.
Tieflings in Faerûn generally have distinct features that differentiate them from other tieflings, such as having fangs or sharp teeth; a forked tongue; or cat-like eyes.