I was a big Planescape fan back in the 90s, and I still think it’s a pretty great. Tieflings were one of my favorite aspects of the setting, though as the years went by the race definitely developed something of a “good drow” problem. While it made perfect sense for there to be a tiefling or two in every party when the game is hopping all over the multiverse, having them all over the place in more traditional fantasy worlds drains a bit of what made them special. That being said, I think the core concept can fit very well with the Appendix N style of DCC.
While many times the strange offspring of wizards and witches may be powerful outright half-demons, there’s definitely something cool to the notion of the slightly off child who becomes more sinister as they grow into their own power.
Tieflings level up as elves in terms of hit points, attack bonus, spells, saves — all of the level-based table stuff covered on p. 58 of the DCC RPG rulebook. They also get Patron Bond/Invoke Patron free as elves do. Due to their nature, they tend very strongly toward aligning with Chaos. In addition, tieflings gain the following abilities.
Second Sight: Because of their otherworldly heritage, tieflings are able to perceive the bonds between worlds. Tieflings can tell if someone is aligned with Law or Chaos just by looking at them. They can also perceive this alignment in magical artifacts.
Immunities: Tieflings are immune to being magically charmed and having their thoughts read.
Sins of the Forebearer: Tieflings begin play with two Minor Corruptions per DCC RPG p. 116 (or from Marks of Chaos 1: Subtle). As they gain power, they display ever more outward signs of their heritage — at every odd level (3, 5, 7, and 9), the tiefling gains another corruption. Roll 1d10 and add the tiefling’s new level: 1-6 Minor, 7-9 Major, 10+ Greater. Luck modifies the result on the corruption table normally, but Luck cannot be spent to avoid gaining the corruption.
Supernatural Sympathy: Because of their connection with the otherworldy, tieflings gain a +2 spell check bonus to all summoning spells and patron spells.
Luck: Tieflings are said to be harbingers of misfortune and ill fate. They gain additional abilities when spending Luck, as follows.
First, tieflings can expend Luck to bring bad luck to others. For every 2 points of Luck expended, the target gains -1 to their roll. The tiefling must be able to see the target or have some part of them (a lock of hair, some toe nails, their wedding ring).
Second, tieflings recover Luck to a limited extent. A tiefling’s Luck score is restored each night by a number of points equal to their level.
OK, here’s the thing — I was originally going to make the bad luck ability a 1-for-1 expenditure, but I was worried that it could be game breaking. I’m still worried it might be a little unbalancing. My main concern is a situation where there’s a party halfing spending Luck to help boost a wizard’s spell while the tielfling is spending luck to reduce the target’s saving throw. Yet there’s another part of me that still prefers the simplicity of a 1-for-1 expenditure. I’d love some thoughts/feedback on this.