|They've activated the self-delete! Nah, I'm just messing with you. |
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.
A dim sun (and relatively bright moon) leave this world forever in darkness. The ground belches up seamingly endless zombies in places, rocks tend to become sharp and twisted over time, instead of rounding and fading away to erosion, and yet life still persists.
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three remain (Swayne the Westking, Hastings the Southking and Lockhart the Eastking), while Vladimir the Northking has been replaced by his lover/apprentice Cornello.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 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 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.