The Shadowfel

The Shadowfel is one of the three mortal-accessible planes in the TDDC cosmos. It was either created by the energies unleashed by Vecna during his battle with Ioun, or these energies corrupted a pre-existing plane of existence. Regardless, the Shadowfel is steeped in Vecna's influence, leading to its being filled with the undead. 
The cursed earth of the Shadowfel is permeated with seemingly endless corpses which are belched forth as shambling zombies. A necromancer is considered to have unlimited access to bodies for reanimation in most parts of the plane’s landmass. Any who are buried there are sure to rise again in short order unless their body is prepared somehow, such as by a special burial rite. The rest of the planar landscape is no less hostile; dark woods, treacherous swamps and fields of strangely jagged, claw-shaped rocks abound. Its inhabitants – mortal and spiritual – are a reflection of their grim surrounds, tending toward the secret and hidden, the parasitic and cruel. Perhaps most disconcerting of all for a visitor from another plane is the oppressive fel sky. The sun and moon provide dim illumination, their light smothered by an omnipresent blanket of clouds, resulting in an eternal twilight. Stranger still, some magical (or perhaps natural) force prevents anyone or anything from getting very far off the ground despite the visible sky above. Specifically, above about 15ft from solid ground moving up requires exponentially increasing effort until approaching a limit around 17ft. It is unknown how teleport or planeshift magic would interact with the Shadowfel’s planar “ceiling”, though it seems unlikely that any attempts to surpass it would be successful. By contrast, the subterranean part of the plane, the Underdark, stretches down beyond mortal imagination, potentially infinitely.
==The main continent==
The surface of the Shadowfel equivalent of The Middle Kingdom is dominated by the five Vampire Kings, who rose to power in times immemorial and wiped out all other vampires. Of the four original Kings, three remain (Swayne the Westking, Hastings the Southking and Lockhart the Eastking), while Vladimir the Northking has been replaced by his lover/apprentice Cornello. Sizable parts of Swayne's and Hasting's territories were seized by Alyssa several thousand (?) years ago.
Each Vampire King runs their territory in a different way, from Swayne ranching humans like cattle and eating one each day to Lockhart allowing nations to form among his slaves, so long as they continue to obey his every edict and send regular tithes of blood.
== The White ==
The White is the area around the north pole of the Shadowfel. The Shadowfel Arctic, if you will.
== The other continents ==
The Shadowfel equivalents of Haroan and Novendil are largely free of the influence of the Kings, since as Vampires they cannot cross running water, including oceans. It is possible for Cornello to cross using the powers of the shackled North Wind, but he chooses not to in case he is somehow dismounted (or the shackle disrupted) while he is crossing.
As a result, other powers hold these continents. They are known to be the main home of the Neogi.
==The Underdark==
The legendary Underdark lies beneath the Shadowfel, of which the subterranean caverns of the Fadelands are but a pale imitation
Drow and tigers and bears, oh my.
Stuff from the recent lore stream.
It is unknown as to whether or not the Drow civilisation is also found below the other continents and if not what else is found in that layer there.