From Morloch Wiki
Throne of Oblivion expansion which contains two new macrozones called the "Plain of Ashes" and the "Bone Marches". The zones consistently only host mobiles of the undead variety, including animated skeletons, ghouls, and Vampires.
Players may not place cities on Oblivion isle.
To reach Oblivion, one must enter the black "Death Gate" which is located on every runegate in the world.