Nightgaunts have a vaguely human shape, but are thin, black, and faceless. Their skin is slick and rubbery. They sport a pair of inward-facing horns on their heads, and have clawed hands and a long barbed tail which is used to "tickle" their victims into submission. They can fly using a set of membranous wings. They make no sound, and are the associated with the Outer God Yibb-Tstll.

Night-gaunts guard Ngranek, an infamous mountain on the isle of Oriab in the Dreamlands. They sometimes capture unwary climbers, tickling them into submission with their claws and barbed tails, and carry them to the lower reaches of the Dreamlands. Nightgaunts are sometimes used as steeds by the ghouls of the deeper Dreamlands, but do not like to fly over bodies of water.