Shadowfell

The Shadowfell is one of the three Material Planes of Somara. It is a dark reflection of the Prime Material Plane, a bleak plane full of decay and death.

Creation
The Shadowfell is thought to have been inadvertently created by Valazar and Syvl. During the First Era, Feyan, Svyl's eldest daughter, asked her father to create a plane for her that lacked many of the things she disliked about the Prime Material Plane, such as darkness, decay, and destruction.

After asking Valazar for aid, he began weaving together the Feywild as Feyan's perceived paradise, removing many of the aspects that she had requested by absent.

However, the removal of many of these things displaced a large amount of negative energy, which eventually managed to coalesce and form the Shadowfell, the dark reflection of the Prime Material Plane and the complete opposite of the Feywild.

Some scholars theorize that some dark power had a guiding hand in the creation of the Shadowfell, believing it highly unlikely that such a large amount of negative energy would simply come together perfectly. This theory, however, has largely no supporting evidence, causing most scholars to reject it out of hand.

Environment
The Shadowfell is a dark, hostile environment. One of the most striking (and immediately obvious) features is the large lack of light - there is no sun, no stars, and no moon in the Shadowfell. The dark sky is an inky black void, sometimes filled with dark grey clouds that bring rain and storms. In addition, light itself seems to have a sort of dampened effect on the plane. Light seems to only travel half the distance that it would in the Prime Material Plane.

Items on the Shadowfell seem to be darkened as well. Color is less vibrant, and creatures and objects there look bleak and lifeless as if the color had been drained out of them. The senses of those on the plane are slightly dulled, as is the taste of different types of food and drink.

Geography
Like the Feywild, the Shadowfell seems to take on a similar geographical structure as that of the Prime Material Plane, with entrances and exits generally corresponding to similar places on the Prime Material Plane. For example, entering the plane from a forest on the Prime Material Plane would generally put you in a forest on the Shadowfell. The continental structure also appears to be the same, with all three planes sharing largely the same arrangement of landmasses.

Unlike the Feywild, however, the Shadowfell seems to follow the same rules of time and space that the Prime Material Plane does. If you were to spend an hour in the Shadowfell, the same amount of time would pass in the Prime Material Plane (though it would be difficult to tell, as without a sun, moon, or stars, it is extremely difficult to accurately judge the passage of time in the Shadowfell).

Curiously, the Shadowfell has a varying relationship with the structure of the Prime Material Plane. Villages and buildings may or may not exist in the Shadowfell in the same place as they do in the Prime Material Plane. For example, if one moves between the planes while inside a castle on the Prime Material Plane, they may find a desolate, ruined copy of the castle on the Shadowfell. It is unknown whether someone on the Shadowfell constructs these buildings or if the Shadowfell simply changes to mimic developments in the Prime Material Plane in certain places.

As a result, it can be difficult to predict where exactly one will emerge if they shift onto the Shadowfell from the Prime Material Plane. Generally, continent and environment will remain the same, but there is the possibility that their portal takes them to some other location, especially if they attempt to move to either plane in a heavily populated area. Research seems to show that the more remote the location of both sides of the portal, the more likely it is to emerge in the same location on the other plane.

As a side note, many locations on the Shadowfell seem to be completely warded against plane shifts, likely the result of the Raven Queen's power.

Inhabitants
The main inhabitants of the Shadowfell are the Shadar-kai, a subrace of elves sworn to the service of the Raven Queen, the mysterious matron who claims ownership of the plane from her seat of power in the Fortess of Memories, located in the Valley of Sorrows, at the heart of the Shadowfell.

Like the Prime Material Plane, the most plentiful race on the Shadowfell are humans. They have small, scattered settlements around the plane, and have similar ancestry to the races of humans on the Prime Material Plane.

The key obstacle preventing the races of the Shadowfell (outside of the Shadar-kai) from establishing large political organizations are the massive amounts of undead that roam the planes. Religious scholars believe that any soul not claimed by the gods will end up in either the Void or rise again in the Shadowfell as an undead being. Shadows, shades, specters, wraiths, zombies, and ghosts are all common. Furthermore, the large deposit of negative energy that the plane is built upon also can attract vampires, liches, bodaks, and other powerful undead, as well as shadow demons.