Cliff-ghasts were approximately half the size of a grown human. They were capable of flight, with leathery wings, and had hooked claws. Their heads were flat and they had wide, frog-like mouths and bulging eyes. They gave off a foul smell.
Cliff-ghasts were scavengers, living off carrion. They also ate Arctic foxes.
Cliff-ghasts communicated with one another using spoken language, though they were not known to speak to other species.
Cliff-ghasts revered the eldest of their kind, a blind ghast whom they called Grandfather. He was respected as a source of knowledge and legend, whose memory went back to before the existence of humans. This Grandfather predicted the 'greatest battle ever fought': the war against the Authority, and that Lord Asriel would win if he were in possession of the subtle knife, called Æsahættr in their tongue.