Originally Posted by Dexai
I guess a "Demonic" subrace Tiefling entry would be nice, even if it's just a generic one.

Fun fact! WotC did actually make a demonic tiefling subrace unearthed arcana that came out with the Rage of Demons storyline to use in the Out of the Abyss campaign. This was in 2015 and they never published it in an official book or even in a companion publication like they did with Genasi and the Elemental Evil storyline.

But you can find it Here