The Shadowfell

the Shadowfell, also known as the Plane of Shadow, was one of the planes of existence in various cosmological models. Its purpose and characteristics evolved as new cosmologies were formulated. Other names for this plane included Shadowland, the Demiplane of Shadow, and simply Shadow.
It existed as sort of counterpart to the Feywild, in the sense that it was a reflection, or "echo", of the Prime Material Plane. Unlike the Feywild, it was a bleak, desolate place full of decay and death.

Type

Dimensional plane

Location under

The Inner Planes