The result of mortal blood mingling with that of powerful evil outsiders, tieflings are clear inheritors of their fiendish forebears.
Most tieflings of Aetheria are descended from the human noble houses of ancient Bael Turath, who colluded with the powers of the Nine Hells to gain the upper hand in their war against the dragonkind of Arkhosia. Those houses were granted Infernal powers and were reshaped into tieflings of hellish blood by Asmodeus himself.
No two tieflings are alike; the fiendish blood in their veins manifests inconsistently, granting them an array of fiendish traits. One tiefling might appear as a human with small horns, a barbed tail, and oddly colored eyes, while another might manifest a mouth of fangs, tiny wings, and claws, and yet another might possess the perpetual smell of blood, foul incenses, and brimstone. Typically, these qualities hearken back in some way to the manner of fiend that spawned the tiefling's bloodline, but even then the admixture of human and fiendish blood is rarely ruled by sane, mortal laws.
As a large majority of the tiefling population of Aetheria descends from the nobility of Bael Turath, some features do appear with relative consistency, especially large horns sprouting from the brow, prehensile tails, and reddish skin.
Since the fall of Bael Turath, the tieflings have had no society to call their own, but instead live alongside humans in their settlements and kingdoms. They tend to live on the fringes of those societies, as their obvious fiendish heritage and the reputation of ancient Bael Turath means that the tieflings are shunned and feared by many humans.
Tieflings face a significant amount of prejudice from most other races, who view them as fiend-spawn, seeds of evil, monsters, and lingering curses placed upon the world. Far too often, civilized races shun or marginalize them, while more monstrous ones simply fear and reject them unless forced or cowed into acceptance.
Tieflings get along best with half-elves and half-orcs, who view their tainted blood as somewhat similar to their own odd bloodlines, and, oddly enough, the dragonborn, as their ancient enemies' tendency to respect both allies and opponents on an individual basis rather than making blanket assumptions makes it easier for a tiefling to establish their own impression.
Alignment and Religion
Despite their fiendish heritage and the insidious influence of prejudice, tieflings can be of any alignment. Many of them fall prey to the dark desires that haunt their psyches, and give in to the seduction of the whispering evil within, yet others steadfastly reject their origins and actively fight against evil lures and the negative assumptions they face from others by performing acts of good. Most, however, strive simply to find their own way in the world.
Though many creatures assume that tieflings worship devils and demons, their religious views are as varied as their physical forms. Individual tieflings can be found in the worship of any of the gods, though they are just as likely to shun religion all together, and many that succumb to the evil in their blood can be found in the worship of all manner of powerful fiends.
Tieflings rarely integrate into the mortal societies they call home. Drawn to the adventuring life as a method of escape, they hope to make a better life for themselves, to prove their freedom from their blood's taint, or to punish a world that fears and rejects them. Tieflings make skilled rogues, powerful wizards and magi, and especially puissant sorcerers and warlocks, as their fiendish blood empowers them. Those who succumb to the evil within often become powerful clerics of fiendish powers.
- Dungeons and Dragons 4th Edition Player's Handbook
- Pathfinder Roleplaying Game Advanced Races Guide