The catoblepas is a four-legged bull-like creature with a very large and heavy head. Because of the weight of its head it can only look down (catoblepas is Greek for "that which looks downward). It has a long mane that hangs over its eyes, which are red and bloodshot. If the beast were ever to look up it would be deadly, because anyone who looks into its eyes will die immediately. It also has a foul and dangerous breath from eating poisonous plants.

The catoblepas may have been based on a traveler's account of the African gnu.