The Shadow Plane is coexistent with the Material Plane and Ethereal Plane. It is a plane where the things born here have their colours, sounds, tastes, and all other forms of perception lessened. Connected to the Material Plane through the Ethereal Plane, much of the Shadow Plane has similar, but distorted, features that can be found in the corresponding place within the Material Plane. Where on the Material a city might exist, on the Plane of Shadow in its place may be ruins or some twisted representation of that city's populace.
In many peoples' minds the Plane of Shadow has very strong ties with undead and for good reason. At the core of the Plane of Shadow resides the Negative Energy Plane which causes the creation of the many undead that exist within the Shadow.