Tiefling

Tiefling appearance is not their fault but the result of an ancient sin, for which Asmodeus wanted all their decedents to know was caused by his infernal influence. But the Prince of Plots ultimately underestimated mortals. Where he wanted his bloodline to be a curse that mortals would recognize his influence, they saw it for what it was; a cruel manipulation of mortal kind attempted by a would be god. No one views Tieflings as the outcasts Asmodeus wished them to be, instead mortals are reminded of how gods can fail.

Infernal Bloodline

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 sclera or pupil. Their skin tones cover the full range of human coloration, but also include various shades of deeper color. Their hair, cascading down from behind their horns, is usually dark, from black or brown to dark red, blue, or purple.

Self-Reliant and Sympathetic

Because of the nature of their bloodline, Tieflings can be descendants from virtually anyone. Many are born of Tiefling parents who themselves had Tiefling parents, but many still have an infernal connection appear after generations of being dormant. Children born as Tiefling to non-Tiefling parents may find a more recent pact is the source of their newfound infernal connection. Empathetic to those whose infernal bloodline may not be immediately known, groups of Tieflings often form in cities and help each other find community in their shared experiences.
Often appearing outside of a homeland, Tieflings know that they have to make their own way in the world and that they have to be strong to survive. They are not quick to trust anyone who claims to be a friend, but when a Tiefling's companions demonstrate that they trust him or her, a Tiefling learns to extend the same trust to them. And once a Tiefling gives someone loyalty, the Tiefling is a friend or ally for life.

Traits

Darkvision. Thanks to your infernal heritage, you have superior vision in dark and dim conditions. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can't discern color in darkness, only shades of gray.
Hellish Resistance. You have resistance to a damage type (your choice).
Infernal Legacy. You know the thaumaturgy cantrip. Once you reach 3rd level, you can cast the hellish rebuke spell with damage matching that of your hellish resistance as a 2nd-level spell with this trait; you regain the ability to cast it when you finish a long rest. Once you reach 5th level, you can also cast the darkness spell once per day with this trait; you regain the ability to cast it when you finish a long rest. Charisma, Intelligence, or Wisdom is your spellcasting ability for these spells.
Languages. You can speak, read, and write Common and Infernal.