A hook horror was a large, bipedal subterranean monstrosity that looked like a vulture-like humanoid with bony hooks in place of hands. It was an invertebrate arthropod that stood about 9 feet tall and weighed around 400 pounds, with a neck of crested feathers and an insectoid chitonous exoskeleton. Hook horrors did not see well at all and were sensitive to bright light, but their hearing and sense of smell was extremely acute. They could produce a high-pitched sonar that enabled them to use echolocation, much like a Bat, to "see" nearby objects and environments without the need for light.
Often found in the Underdark or extensive cave systems, they possessed a rudimentary intelligence and language. Hook horrors typically lived in families of up to twelve, led by their eldest female, and slept for nearly twelve hours a day. They were an omnivorous species, though they preferred the meat of whatever creatures they could catch. They would resort to fungi or lichens if they could not obtain meat, as their hooked limbs gave them excellent purchase when climbing rocky surfaces. This same ability gave them strong ability to ambush prey from above, and they would hunt in packs while ambushing from above.