Tieflings. Somehow, they’ve gone from being the result of hot demon-on-human sex to being a race of emo posers. Hell, they even dropped the whole idea of Yeenoghu or Orcus or the occasional Marilith getting their freak on with some cultists, and instead there’s some vague "bargain" struck in the equally vague (but still intrusive and annoying) "assumed world", which exists — and this is official, mind you — so that artists at WOTC will know what holy symbols to paint. Seriously. This was one of the excuses given for the presence of the "default" world. Well, that, and certain people on the design team are rumored to hate worldbuilding with the burning passion of a thousand suns, and seem to think that getting back to the days of "You’re in the Town of Vyllaj, and just outside the town is the Dungeon of Danger. Click ‘1’ to visit the Shopkeeper. Click ‘2’ to visit the Tavern. Click ‘3’ to enter the Dungeon." is a really good idea.
I say thee NAY!
In my world — yes, WOTC, I said "my" world. Mine. Not yours. Can not have. — Tieflings are very much the result of doing the nasty with things that are nasty. Though this happened ages past (like all good sexual revolutions, it was either before your time or after you were too old to take part), the consequences (namely, Tieflings) are still with us. They are not a race, they are the occasional reminders of that ancient time. It was called variously the Age of Demons, the Demonwar, the Elfwar, or the "time when the Aeld screwed over the whole world". Huge amount of backstory short (You think players telling you about their PCs are bad? Never get a DM started on his world!), a bunch of hoity-toity folks with pointy ears thought summoning and binding mere Type II Demons wasn’t enough — they were going to get Demogorgon, Jubilex, et al to play Steppin Fetchit for them. It didn’t work. They rebelled. They evolved. They had a plan. (Said plan was "Tear the world to pieces and dance in the bloody ruins while frothing in a mad rage", but, hey, it was still a plan!) Eventually, the bad doobies were sent back to the Abyss, but the consequences of their rampage across the mortal world remain, from the introduction of demon-bred races like gnolls and minotaurs, to a dark, festering, seed of chaos and evil lurking in the bloodline of man. (That woud be the Tieflings, in case you forgot where I was going with this while I digressed madly.)
Anyway, since there’s lots of Demon Princes, it only makes sense that Tieflings would sometimes show traits relating to their special ancestry.
Read on for more!