Tieflings are either born in the Lower Planes or have fiendish ancestors who originated there. A tiefling is linked by blood to a devil, a demon, or some other Fiend. This connection to the Lower Planes is the tiefling’s fiendish legacy, which comes with the promise of power yet has no effect on the tiefling’s moral outlook.
A tiefling chooses whether to embrace or lament their fiendish legacy (lineage).