From publisher blurb:
Welcome to Template Races: Tiefling. Tieflings, also known as devilspawn or hellspawn, have become a staple of our fantasy roleplaying games. The concept of a mortal character with a fiendish ancestry is one that is popular with a lot of players. A lot of work has been put into providing a variety of fiendish heritages for tieflings. However, the tiefling’s mortal ancestry is almost always restricted to being human, or just hand waved away as “sure you can have an elf tiefling, but it is the fiendish part that is important”. Have you ever wanted to play an elf tiefling that is actually elfy?
That is where the tiefling race template comes in – it is a quick and relatively simple way to produce game rules for tiefling races that incorporate elements from the mortal race as well as their fiendish heritage. Here we present the tiefling race template and over a dozen examples of tiefling races. Use this race template to combine tiefling racial traits with the racial traits of the desired mortal race in a similar manner to applying a monster template to a monster stat block.