Creatures that haunt the deepest and darkest chasms of the Dimension of Dreams, floating between the Dreaming and the Ethereal Plane, and occasionally slipping through the shadows onto the Material Plane. They delight in tormenting mortals, and their typical means of killing them is to grab them by the claws, fly them a hundred feet in the air, tickle them with their tail, and drop them. They boast a very high grapple check and a horribly efficient tail. Immune to cold damage.
The creature Gull heard flying about in the East Courtyard of Briarstone Asylum early in Act I was likely a Nightgaunt, but the first face-to-face encounter with one happened in the North Courtyard in Chapter 27.
In Chapters 113 & 114, four of the creatures ambushed the Sellen Starling while it sailed the Glass River inside a bank of supernatural fog. (In Chapter 123, it was learned that they had been brought over from the Dreamlands by Vadrack) Dora recalled at that time that their tickle ability is a swift action to nauseate a grappled or helpless foe against a Fortitude save. Does not breathe, see, or smell, and is immune to effects based on those senses.
First Reference: Chapter 27
Other Notable References: Chapter 113, Chapter 114, Chapter 123