Aasimar are planetouched beings: children of humans, who manifest celestial heritage from generations past. Their ancestors vary in type, from trumpet archons to couatls to servants of deities and whatever else inhabits the good-alinged planes. Aasimar generally have one distinguishing feature which sets them apart from normal people. These are related to the kind of outsider they descend from, and include traits such as silver hair, emerald skin, small feathers somewhere on their body, small patches of iridescent scales or a strong, clear voice.

Aasimar are rare and therefore have no society of their own. They are regarded as strange outsiders in most places, which can be very frustrating to aasimar who just wish to blend in. Many have become cautious and distant towards humans because of this, and get along better with other halfbreeds, such as half-elves. Due to their heritage, most aasimar feel the pull of the divine strongly, and become clerics, or paladins if their ancestor was a lawful creature. Even those who stick to mundane careers are usually compelled to do good by their very nature. Evil aasimar, disappointed and embittered by how lesser beings treat them, are not completely unheard of.

Most aasimar on Faerûn trace their bloodlines to the incarnations of Mulhorandi deities and their noble offspring. Through marriage, the blood of Mulhorandi deities spread far and wide. It's common for these aasimar to serve the deity they descend from, and to feel affection for the type of animal that symbolizes their deific ancestor. There are more aasimar in Mulhorand, Unther and Chessenta than anywhere else on Toril, as aasimar with different descent are relatively random cases with no common origin.