I am am having problems finding aasimars mentioned in any other way outside of dungeons and dragons. Did Wizards of the Coast (or TSR whatever) invent them, or are they based on any mythological creatures or other works.
An aasimar is creature between an angel and a human. In D&D they are something above just a planar touched human someone with a celestial in their ancestry, and a a half celestial, someone with an celestial parent.
The creature does not have have anything to do with the Christian idea of an angel, just some association with the force of good in the universe.