Shadowfell

"Everything in this place looks like a shade, a pale shadow of what it should really be. It's revolting, but its power is undeniable".
In the middle of the Silver Age, a Sorceress had made her way into this Plane, which at the time had been ruled over by a Tartarus Demon known as Xalgran. Xalgran had been impressed by this Sorceress and decided to make her his consort, only to be slain by her after she took control of his shades. She absorbed his essence, turning her into the New Ruler of Shadowfell, The Raven Queen. A being that could be compared to a minor god. She belongs to the Domain of Death, much like Thanatos, and as such despises undead, viewing them as abominations.

Manifestation

Everything looks like a shade of its real self in the Material Plane. People look like soulless silhouettes, Dragons become warped into abominations that embrace the sick darkness, everything that should be living, is simply not.
The most striking and immediate impression a visitor to the Plane of Shadow experienced was the lack of color and light; no sun, moon, or stars adorned the vault of the inky black sky, and all things looked as if the color had leeched out, leaving nothing but black and white, which in the dimness were more like "dark black" and "light black". A light source only illuminated half the distance it normally would, flames and fires put out less heat, and spells that dealt with light or fire were less predictable and prone to failure, whereas shadow spells were enhanced. On the other hand, although it would not illuminate as far, any light source on the plane could be spotted at a distance of up to ten times its normal range of illumination, such was the contrast to the constant gloom, similar to a star in the night sky. Even a light source that only put out shadowy illumination, like a darkness spell or a lantern burning shadowlight oil, could be seen up to five times its range of illumination.

Localization

Also known as the Plane of Shadow, it is a realm born of the power of Tartarus, the Abyss, meant to reflect the Material Plane in an ugly and dark mirror image which would corrupt any creature that stayed in it for an extended period of time, with very few exceptions. It was not created on purpose.
It can be accessed through magical rifts that are created on purpose. Accidental pockets of Shadowfell are unheard of.

Type

Metaphysical, Demonic