Tiefling

To be greeted with stares and whispers, some to suffer violence and insult on the street, to see mistrust and fear in every eye: this is the lot of the tiefling. And to twist the knife, tieflings know that this is because a pact struck generations ago infused the essence of Asmodeus—overlord of the Nine Hells—into their bloodline. Their appearance and their nature are not their fault but the result of an ancient sin, for which they and their children and their children’s children will be held accountable. But there is a glimmer of hope that could see the tiefling peoples share a home, and release from their infernal heritage.

Infernal Bloodlines

Tieflings are derived from Human bloodlines, and in the broadest possible sense, they still look human. However, their infernal heritage has left a clear imprint on their appearance. Tieflings have large horns that take any of a variety of shapes: some have curling horns like a ram, others have straight and tall horns like a gazelle’s, and some spiral upward like an antelopes’ horns. They have thick tails, four to five feet long, which lash or coil around their legs when they get upset or nervous. Their canine teeth are sharply pointed, and their eyes are solid colors—black, red, white, silver, or gold—with no visible whites or pupil. Their skin tones cover the full range of human coloration, but also include various shades of red. Their hair, cascading down from behind their horns, is usually dark, from black or brown to dark red, blue, or purple. A Tiefling can expect to live to around 120 years of age. Tieflings can be born to human parents, if those parents or their ancestors have either made a bargain with a devil. Any union in which one parent is Tiefling will result in a tiefling child.

Self-Reliant and Suspicious

Being up until recently a stateless people; Tieflings had often subsisted in small communities found mostly in human cities or towns. These small communities are often in the roughest quarters of those places, where they grow up to be swindlers, thieves, or crime lords. But this is a product of environment, not nature. Others, who have had the opportunity to escape poverty, particularly as merchants, performers, or in employment of the military for example; have created their own small enclaves which garner great respect from the people around them. Tieflings have existed within human lands for a long time, and proved their value and trustworthiness; but mistrust and racism runs deep in some places; so Tieflings continue to encounter marginalization in their lives. As a result of their upbringings, many Tieflings are extremely resourceful, self-reliant, and have a very strong bond with the community (usually made of a handful of families) they grew up in.

Powers and Abilities

Many tieflings are very charismatic and are also quite intelligent. Due to their devilish ancestry, tieflings are resistant to fire and can see in dim light and darkness. Their infernal legacy grants them a small number of magically abilities, including amplifying their voice, changing their eye color, and minor manipulation of fire. More powerful tieflings can wreath their enemies in fire if they are attacked and can create pockets of magical darkness

Origins and Society

Tieflings are thought to have been created in a city now gone called Issylra sometime during the 2nd Epoch by a cabal of warlocks seeking to gain more otherworldly power. As a result of this bargain, their children were marked with the fiendish influence of their masters. An alternative theory suggests that the first tieflings were created in the city of Kamordah in Tyrean, as a result of the cities inhabitants tying their bloodlines to Asmodeus in exchange for magical knowledge. Some look to the high population of Tieflings in the Meridian Concord as justification for this.
Like other races that were the result of the breeding of two or more others, tieflings had no true culture they could call their own. However, there were many archetypal features of tieflings that were not necessarily innate. This include their attitude regarding their heritage, and while some tieflings embraced it, others were repulsed by it, forging the two most common stereotypes of tiefling.
Tieflings can be found across the entire civilized world, but most commonly in Human lands, and more towards the heavily populated areas. Few willing choose to live in small towns where they can't blend it away from those who are uncomfortable with their mixed reputation and diabolic heritage.
Lightforged Republic of Morencia - Prior to 2787 5e, the Tieflings were a stateless people. But after several years of hiding, and support from the then hidden Elven Realm of Thas'Dorah, they declared independence from the Kingdom of Tiriande. They were lead to this place, by a new religion called the Guiding Light, which a being of great holy power promised to break their diabolic heritage, and being them into the light. The region of Morencia within Tiriande is mostly an arid, grassy plateau south of the Donark Mountains, and west of the dry canyon network known as The Scar, and ends at the sea mostly in grand cliffs hundreds of feet high.
There are three major cities in Morencia:
Freehold Port - Is the largest city in Morencia, built into the rocky cliffside of a natural harbour and the River Pilt as it streams over the cliffs into the habour. Freehold is grand lively city where all manner of races can be found, and the city prides itself on its varied and accepting culture. It’s a city teeming with life and excitement, but also a strong seedy underbelly. Roughly 40% of the population here in Freehold is now Tieflings.
Ember Cairn - Now the largest Dragonborn settlement in Esseas. Built on the edge of the arid canyon bordering the east, it overlooks the canyons and out into the endless golden sea. Once the oldest Dragonborn colony, the site has taken on near religious importance to them. Despite this, Tieflings still make up a large portion of the population within the city along with humans.
Whiterock - Is both the spiritual and political capital of this fledgling kingdom. It was built nearly from the ground up out of gleaming white marble and stone on the very hills where the first Tieflings founded the Guiding Light and granted freedom from their diabolic heritage. The city at the same time a home, a grand temple, and a fortress. The majority of the population is Tiefling, but there is also a sizeable Dragonborn and Human population of converts to this new religion.
https://www.dndbeyond.com/races/tiefling - for stats and rules