Tieflings

Tieflings are humans with traces of fiendish ancestry. Although a few tieflings manage to overcome their ancestry and remain good and trustworthy individuals, most follow the dark urges tugging at them, becoming selfish, cruel, and evil as they mature. Those that do not must constantly struggle against thoughts of violence and corruption, seldom knowing the peace that many other good-aligned creatures take for granted. Tieflings are stealthy, deceptive, and often selfish. Trusted by few, they in turn trust no one, knowing that, no matter their behaviour, they'll likely be suspected of wrongdoing as soon as any problem arises in the community. Because of such hard lessons in dealing with other races, tieflings are suspicious of kindness and almost never trust that a member of another race will remain loyal or friendly once the tiefling's ancestry is known.
Many tieflings are indistinguishable from humans. Others have small horns, pointed teeth, red eyes, a whiff of brimstone about them, or even cloven feet. No two tieflings are the same. Tieflings are sneaky, subtle, and generally conniving. They prefer to strike from ambush and usually avoid a fair fight if they can.
In 1358 DR, a warlock coven known as the Toril thirteen performed a ritual that cursed most tiefling lineages—those of demons, devils, hags, and rakshasas, among others—with the "blood of Asmodeus", changing their original lineage with that of the archdevil himself. This was done to make Asmodeus a "racial god", ensuring him enough followers to attain godly powers. After the Spellplague of 1385 DR, when Asmodeus became a god, the magic of the ritual took effect across all of Toril and afterwards most tieflings living in the 15th century DR were of the Asmodean lineage, all having a similar devilish appearance.
Prior to Asmodeus's ascension to godhood, the infernal blood could be diluted through intermarriage, but afterward, the union of a tiefling with another race always produced a tiefling child.
In the late years of the 15th century, tieflings of other bloodlines began to be born again, but the Asmodean lineage was still the most numerous by a wide margin at the time.

• Cold, Electricity, Fire and Poison Resistance

Tieflings subtract 5 points of damage, to a minimum of zero, against cold, electric, fire, and poison attacks and effects. They also receive a +2 bonus to all saving throws against cold, electric, fire, and poison attacks and effects.

• Darkvision

Tieflings can see in complete darkness for up to 60 feet. Darkvision produces images that are in shades of gray, but it is otherwise like normal sight. Tieflings can function well with no light at all. Bright lights, such as from a lantern or other light source, spoil darkvision. A tiefling requires one turn to adjust his or her eyes when a light source is extinguished before gaining full use of darkvision.

• Darkness

A tiefling can use darkness once per day as a 1st-level caster or a caster of her class level, whichever is higher.

• Languages

Common and Infernal plus one language per point of Intelligence bonus: Draconic, Dwarf, Elf, Gnome, Goblin, Halfling

• Size

Medium

• Movement

30 feet

• Typical Classes

Assassin, Bard, Cleric, Fighter, Illusionist, Rogue, Wizard

• Attribute Modifiers

+1 Dexterity, +1 Intelligence, -1 Charisma

• Ability Modifiers

+1 decipher script, +1 find traps, +2 hide, +2 move silently