The refugees from Elturel are indeed a special case, we'll get into them, but first, background:
Tieflings first appeared in 2e, the the Planescape Campaign Setting, as two of the main new "planetouched" races (the second being Aasimar).
in 2e, and 3e, They are literally just part-fiends (devils and demons are fiends, but there are more than just them). Cambions and Alu-fiends are both forms of half-fiends, but if a half-fiend has a baby with a human, it'll most likely be a Tiefling. Fiend blood at 1\4 or less = Tiefling. Di'Terlizzi style Tieflings like Doric were the norm, and they were described as being mostly human, but with a few fiendish appearance traits, and the roll table for those different traits was MASSIVE. The reason Doric was most likely abandoned, is that back then it was possible for the fiend blood to become very diluted over time, to the point were people might not even know they had fiend blood, and then suddenly, oops! Tiefling baby! Looks like one of you had an ancestor who dallied with fiends. I've used that exact orphan plot for a character in a past game.
Honestly the Preferred version, every Tiefling PC, I made in D&D 5e was this type, 4e ruin everything with their stupid Pact Garbage, I just want my Devil race who are biologically related to Devils,
However what I don't want is waterdowned humans who were transformed by grand daddy's pact, because WoTC decided to fuck up one of their coolest races for no apparent reason, This Pact garbage makes me want Playable Cambions despite them being OP at least they're still related to Devils aka the whole point of playing a Tiefling character in the first place.
