Halosians were large bipedal, vulture-like creatures. Their cranium was small, and their head had a long, sharp beak. They possessed wings, the spans of which were easily eight feet when fully stretched, but Halosians also had thin arms and articulate claws with which to operate machinery. They often have a very necrotic appearance, with exposed sinews on the mouth and a lack of tissue underneath the jaw.
Their wings appeared to be vestigial only, as the creatures were seemingly too large to use them for actual flight.
The Halosian society seemed to be a class-oriented one. Each individual's main goal was to "evolve" up the class structure by increasing his or her number of hostile kills (though the opponent may be peaceful). They employed large battleships with weapons that fired energy pulses. Their code allowed mutiny if the captain, or lord, failed, at which point other members of the crew could take charge and evolve themselves. Their vomit was acidic, self-mobile, and highly destructive.
The Halosians' resemblance to the Skeksis, the villains of the Jim Henson Company film The Dark Crystal, is not coincidental: the frameworks of the Skeksis puppets still existed and were reused for the Halosians. (
- (2.09 "Out of Their Minds")