Gloomstalker

The gloomstalker is a race of flying monsters created by Matthew Mercer. They are first encountered by Vox Machina in the Shadowfell, above the city of Thar Amphala.

Appearance
"Black as night against the gray sky. From this distance, you make out no details in their bodies. It's almost like a moving shadow above you. Wherever light would hit to give you some sense of structure, it's just absence, void. It's just a flying shadow."

"It is billowing black shadow like smoke off of it. You can see glimpses of some sort of physical form in there, but it's so blurry, it's almost like it's phasing between physical matter and dream. You're not sure what it's made from, but you can see what looks to be an elongated neck, some sort of snapping jaw at the end, and two bright, greenish-yellow glowing beacons like eyes at the front of its face. Its wings don't have skin or flesh, it's just dark smoke, and as it flaps, it leaves these trails, these curling bits like black, black, black smoke. ... It's wyvern sized. It's maybe 20 feet from wingtip to wingtip."

Behavior
One of the gloomstalkers encountered by Vox Machina shows evidence of being able to dispel an illusion of a little girl, produced by Scanlan. However, the gloomstalker is not intelligent enough to understand why the little girl disappears when its anti-glamor cone crosses her.