The Shadowfell

The Shadowfell is a plane of existence which runs parallel to the Prime Material Plane in the Great Prism cosmology. It is a dead, barren world characterized by entropy and decay; it is believed in many religions that all mortal souls pass through the Plane of Shadow on their way to the unknowable afterlife.

Characteristics

As a void and barren plane, the Shadowfell is characterized by its apparent absence of life: the only plants that grow in the Plane of Shadow are black and withered, the sunless grey sky and rolling dark clouds above providing them no nourishment. The air is thick with drifting ash and cinders, and occasionally a planar visitor may hear the faint whispers of voices carried on the wind.
Perhaps most curiously, throughout the expansive wastes of the Shadowfell, one might find the ruins of huge buildings and structures of unknown make or origin. For the select few arcane scholars lucky (or unlucky) enough to have visited the Shadowfell, the creation of these structures has led to a number of speculative theories: according to some, the existence of these structures indicates that what is now known as the Shadowfell may not have always been the desolate plane of existence it is now; alternatively, others hypothesize that as a plane of death and entropy, the Shadowfell merely takes on the appearance of the most recent world that has succumbed to its decay.

Inhabitants

Among many of the faiths of Teranuz, it is a widely held belief that the Shadowfell is a transitional space, where the souls of recently deceased mortals must travel through on their way to whatever awaits them on the other side. Occasionally, these departed souls are unable to finish this final leg of their journey and become trapped in the Plane of Shadow, where they eventually twist and mutate into grotesque undead.
The transformative effect of the plane's necrotic energy can have an effect on living creatures as well; visitors from other planes that spend an extended amount of time within the Shadowfell may also find themselves altered by the strange landscape. In a best-case scenario, the individual may tap into the necrotic powers of the plane to unlock strange new abilities; it is far more likely, however, that they are twisted beyond recognition into a strange and unsightly abomination.
Because interpretations of the Shadowfell factor into many religions, a number of them also interpret the plane as the home of their faith's respective psychopomps and deities which reside over the domain of death. However, if there are living gods within the Shadowfell, none have ever encountered one and lived to recount the experience.

Type

Dimensional plane