The Shadowfell
The Shadowfell, also known as the Plane of Shadow, is an echo of the Prime Material Plane suffused with negative energy and elements of it are used to funnel the transition of souls from life to death or back. It exists as a counterpart to the Feywild, but unlike the latter, it is a bleak, desolate place full of decay and death. The Realm of Eltharel, the goddess of Death and the Afterlife, is known as the Citadel of Remembrance and is tucked into a corner of the Shadowfell where the Gray Lady passes judgement over mortal souls.
Traveling to the Shadowfell is fairly easy and there are many places where an adventurer can slip into the shadows and find themselves standing in this grim plane. The most common places to find these Shadow Crossings are in graveyards, battlefields, and in the bleak corners of crypts, though the crossings never last very long. It is as if the plane is boiling over, and the bubbles rise and burst into the Material Plane.
These crossings may last a day, hours, or years, though the moment that the sun touches on them they burn away. Many of these same crossings are one way, and once one arrives in the Shadowfell, one must find another way home. Sometimes these crossings will only expel shadow-creatures on to the Material Plane before closing. Many communities have been wiped out when a Shadow Crossing appeared in their graveyard, causing the dead to rise.
The most striking and immediate impression a visitor to the Shadowfell experiences is the lack of color and light, leaving nothing but black and white. A light source only illuminates half the distance it normally does, flames and fires put out less heat,and spells that deal with light or fire are prone to failure, whereas shadow spells are enhanced. On the other hand, although it does not illuminate as far, any light source on the plane can be spotted at a distance of up to ten times its normal range of illumination; such is the contrast to the constant gloom, similar to a star in the night sky.
Gravity and time are the same on the Shadowfell as on the Prime, but the Shadowfell is magically morphic, and likes to change - parts continually flowing to other planes. Consequently, precise maps are useless, as they will probably be inaccurate by the time that they are finished.
Iis landscape is a dark, twisted echo of what exists on the Prime. Landmarks are usually recognizable but altered in some bizarre way: buildings might be constructed in a different style, built with different materials, at a different location, and/or in any condition from dilapidated ruins to its normal appearance, or otherwise strange and distorted.
Other less dangerous but quite unsettling echoes occurr in areas analogous to towns and cities in the Prime Material Plane. They are nothing more than mirages, but familiar faces and places seen through the macabre mirror of the Shadowfell can be very demoralizing. Structures might appear altered, dislocated, destroyed, or replaced entirely by something else. Mirages of the living have visages of distorted nightmares, but are still recognizable enough to give travelers a jolt of fear and revulsion.
Air, water, and food exist on this plane, supporting plants, animals. Visitors can survive indefinitely if they are willing to endure thick, foul-smelling water, food that oozes dark blood, and a nip of cold in the air. A visitor can never feel warm, often hears or senses the presence of things that aren't there, and can never shake the feeling of being watched. It is a constantly unsettling place. Over time, exposure to the Shadowfell alters living things, and emotions and the ability to experience them seems to fade over time.