In Dungeons and Dragons, Tieflings are mortals with demon blood. So, you might think that they — like D&D’s other ancestries — have supernaturally long lives. You would be wrong.
- 5th Edition: A few years longer than humans.
- 4th edition: Lifespan not mentioned, assume same as humans.
- 3rd edition: Lifespan not mentioned, assume same as humans.
- 2nd edition: Lifespan not mentioned, assume same as humans.
- 1st edition: Tieflings do not exist.
In 5e Dungeons and Dragons tieflings age as humans but “live a few years longer” (2014 PhB, page 43). There’s not much other lore, but the introductory quote is from a 4e tie-in novel and parts of the body text are copy-pasted from the 4e Player’s Handbook.
In 4e and 3e the tiefling maximum lifespan isn’t mentioned and can be assumed to be the same as that of a human. Note that these two editions do give different accounts of how tieflings came to be:
In 4e tieflings are the descendants of the ruling class of an ancient evil empire who made a blood pact with demon lord and were transformed (which might remind you of the classic orc storyline from Warcraft 3).
In 3e (and earlier) tieflings are people with at least one fiendish ancestor: that is, a demon, a daemon, or a devil, which are different things, because D&D.
Neither origin has any direct impact on their lifespan, but they both provide different plot hooks if you’re looking to justify some ancient tiefling NPC.
In 2e lifespan limits aren’t mentioned either, per the Planescape Player’s Guide, part of the Planescape Campaign Setting box set, page 12. However, it is mentioned that some people can and do mistake tieflings for ordinary humans.
In 1e tieflings don’t exist, but the second Monster Manual has two things that are pretty similar buried in the Demon section (Monster Manual II, pages 35-37), called alu-demons and cambions.
Alu-Demons are the daughters of succubi and mortal men. Their lifespans aren’t mentioned, but they tend to have very high stats and a fifth of them aren’t evil (Lost Caverns of Tsojcanth, page 5).
Cambions are the sons of male demons and mortal women. They don’t have a mentioned lifespan either, and their powers depend on their father’s rank in the Abyss. The cambion Iuz is a pretty major villain in the World of Greyhawk setting.
In 2e and 3e lore, any given tiefling could have a cambion or an alu-demon as a parent or grandparent.
