The Aenar were physiologically very similar to the Andorians. Like Andorians, they had two antennae, although those of the Aenar had small indentations in the funnel-shaped tips. They had no skin or hair pigmentation, resulting in a pale ice-blue/white appearance similar to Human albinos. The most distinctive trait of the Aenar were their highly evolved telepathic abilities. An Aenar was capable of reading minds and of psychically projecting itself to other humanoids. They used telepathy to communicate amongst themselves. Many, if not all, Aenar were completely blind yet had the ability to "see" via telepathy.
The Aenar of the 22nd century lived in an underground compound on Andoria shielded by a dampening field. They had no leader, but would appoint an authorized delegate known as a Speaker if a situation warranted it. The Aenar had a strict law against reading the minds of other people without prior consent. They had a strictly pacifist ideology and deplored violence.
The Aenar were considered a myth in Andorian society until 2104, when the Andorians rediscovered the Aenar living in the Northern Wastes of Andoria. Afterwards, the Aenar maintained diplomatic contact with the Andorian government, though they remained extremely secretive. Shran claimed he could count on one hand the number of Andorians who had seen one face-to-face.
In 2154, the Aenar became involved in interstellar affairs when one individual, Gareb, was kidnapped by the Romulan Star Empire. Using telepresence, the Romulans used Gareb to remotely pilot an experimental drone ship.
- See: Unnamed Aenar
Though the appearance and existence of the Aenar was not revealed on-screen until the final scene of "United", the final draft script of immediately previous episode "Babel One" described them as "a new Andorian sub-species" whose "skin tone resembles that of an albino." The final draft script of "United" elaborated on this, establishing the Aenar as not only "albino Andorian[s]" with "dead white skin" but also referring to them as having "milky eyes". The episode which focuses on the Aenar the most is the next episode, "The Aenar". In that episode's final draft script, the pronunciation of the group's name was phonetically notated "EE-nar".
It was not specified that the Aenar became members of the Federation as the Andorians had done, although this seems likely given that they were native to the same moon as a founding member. In TNG: "Attached", Captain Jean-Luc Picard explained that every member of the Federation (as of 2370) had "entered as a unified world."