This description remained true in 3rd Edition. In further supplements it was clarified that Tieflings were usually descended from fiends but not the same manner as half-fiends, since a Tiefling's fiendish ancestry lies further up the family tree.
In the Planescape setting, where Tieflings were introduced, they were described as being a mixture of human and 'something else' with the implication that the medium-sized non-human ancestors originated from the evil 'lower planes'. Originally introduced in the Planescape campaign setting in the second edition of Advanced Dungeons & Dragons, they became one of the primary races available for player characters in the fourth edition of the game.
The tiefling ( / ˈ t i f l ɪ ŋ/ TEE-fling) is a fictional humanoid race in the Dungeons & Dragons ( D&D) fantasy roleplaying game. Fictional humanoid race in Dungeons & Dragons