Can I play a tiefling?

"Do you have tieflings?" is a question I got asked when I made elevator pitch elevator pitch of Scarterra to strangers who happen to be D&D players or ex-players. ]Tieflings are popular character choices.
No, Scarterra doesn't have tieflings in it.
This is not simply to avoid a lawsuit from Wizards of the Coast. Tieflings in D&D are normally descendants of devils or fiends. Scarterra doesn't have devils or fiends, so it cannot have tieflings in this sense.
Scarterra does not have devils or fiends (and it doesn't have celestials either) but it does have spirits. Scarterran spirits are the servants of the Nine but they are not automatons or slaves of the Nine. They can act on their own to an extant and sometimes "acting on their own" means having sex with a mortal and conceiving a half-spirit offspring. And the children and grandchildren of half-spirits can retain noticeably traits from their spirit ancestor.
Scarterran Fair Folk also can have sex mortals and create legacies of children with otherworldly traits. In fact, Scarterran Fair Folk are even more promiscuous than Scarterran spirits.
Some of these spirit or faerie legacies might have horns, devil tails, odd skin coloration, a missing shadow, and pointy teeth, like a tiefling. That said, a player can pick almost ANY otherworldly traits they want (assuming the GM approves). These traits do not have to be tiefling-adjacent. The Merits and Flaws system of Scarterra lets you customize what otherworldly traits your character has.
If you want to play a character that is discriminated against for his/her otherworldly heritage, you can do that with Social Flaws. If you want a character with special connections or respect from their otherworldly heritage you can take Social Merits.
If you just want to play a sexy character with horns you can play a satyr?. They have horns and goat legs like many tieflings. You can even play a satyr with unusual skin tone and hair color depending on your character's elemental ethnicity. If you don't want to shell out ten freebie points to play a satyr, you can play a half-satyr which is basically a half-elf with a point or two of distinctive appearance. You can even play a satyr that is a spirit or fae legacy.