Gloomwing moths looked like giant moths, their body and wings covered in geometric patterns of black and silver. The geometric patterns glimmered naturally. Their antennae resembled large, black ferns. They had eight legs, each ending in a sharp claw, and a double pair of large mandibles.
Gloomwing moths had the innate ability to duplicate the effects of the confusion spell. When a sentient creature looked at a gloomwing moth, its geometric patterns caused the creature to become confused' Thanks to these same geometric patterns on its body, a gloomwing was perfectly camouflaged in darkness or near-dark conditions.
Gloomwing moths hunted prey in darkness. It was capable of simply grabbing and flying off with smaller creatures up to 3 ft (0.91 m) in height. Against larger prey, it attacked while hovering, lashing out with their claws. It could summon other gloomwing moths by releasing a pheromone, which also weakened other creatures within 25 feet (7.6 meters).
Gloomwing moths were solitary creatures, only gathering in groups to hunt large prey. Gloomwing moths were in fact the final stage of growth for tenebrous worms and only lived for several weeks. Their life was simple, consisting of hunting prey to eat, and finding a mate. Female gloomwing moths laid up to ten eggs on the corpse of another creature. After twelve days, tenebrous worms emerged from their eggs and began feeding on the corpse.