Orcus¶
Lord of the Undead
Orcus is a demon prince who "commanded legions of the dead during the Demon Wars" and "was able to raise whole armies of dead instantaneously from the battlefields" (S434, S372). Too powerful for the Abyss to hold, he rules a kingdom of the undead in the Underdark, and in the Fifth Age he holds, without knowing it, a piece of the Mithis Heartstone.
The Demon Wars and after¶
In the Demon Wars Orcus led the dead. When the demons were bound to the Abyss, he was one of those who could not be: "Orcus is too powerful to be imprisoned in the weakened Abyss and currently rules a large kingdom of undead in the underdark north and east of Gur'Turra" (S434, S372), the dwarven fortress of Gor'Turra. Unlike Gothmog, who escaped his prison and vanished, Orcus is not said to have been imprisoned at all.
Rank¶
The demon classifications place Orcus with Gothmog in the rank of Demon Prince, second only to the seven archdemons (S114, S518, S512). The demi-god lists count him among the lesser demi-gods, alongside Gothmog and Vinias (S434). See Archdemons and Undead.1
The Axe of the High King¶
In the Fifth Age, Orcus possesses the Kalamite Axe of the High King, the part of the Mithis Heartstone associated with Khardas, "lost somewhere in Kahun'Darahl," the fallen dwarven capital whose ruins have their page at Kahun'Darahl. He "doesn't realize what he has. He is suppressing it because it creates an unwanted hollow" (S182). The same notes call him "a Demon Prince of ???", leaving the archdemon he serves, if any, unnamed. The search for the Heartstone's pieces belongs to the Sancturi Campaign.
Gap
The sources do not describe Orcus's appearance, the extent or cities of his undead kingdom, whom he serves, or whether Kahun'Darahl lies within his kingdom. Whether he ever met the dwarves of Gor'Turra in war is not said.