Ephemeral

Ephemerals, also called ephemeras, were a class of outsider native to the Plane of Shadow. They included the predatory, two-headed reptilian dusk beast; the ethereal, six-legged equine ecalypse; and the dark and deadly plane-shifting tree called the umbral banyan. Although very different, all were partially or wholly composed of shadow-stuff. They usually lurked near vortices to the Plane of Shadow and sometimes wandered or were taken onto other planes, where they were employed as hunters, mounts, or guardians.

Notable Ephemerals
In the Year of Lightning Storms, 1374 DR, a dusk beast named Grask served as companion to the shadar-kai Sithierel on the Necreme as they plied the Shadow Swamp in the Plane of Shadow. It was presumed destroyed by adventurers in service to Mystra in early Eleint. Dusk beasts were also possibly found wild in the swamp.