Abaddon Plane
As the physical embodiment of death, the daemons exist in a state of constant predatory conflict, only granting their service to the plane's leaders, the Four Horsemen of the Apocalypse: Death, Famine, Pestilence, and War. Settlements are rare and far between, with most specializing in the soul trade or the sale of items designed for differing types of murder, ranging from single targets to mass extinction events.
Of all the deific powers to change during the events of the Gap, few were as affected as the ranks of the daemonic harbingers. These demigod daemons typically swear fealty to one of the Horsemen, but some remain independent and try to establish broad power bases long enough to seize power. Rising harbingers, like Firjadah the Twisted Screen Name or Batwahr the Creeping Fallout, establish themselves as personifications of death related to modern innovations. Of the older harbingers, the Prince of the Wracked, Roqorolos, once served Apollyon but has since disappeared and turned his attention to the mortal Universe. This harbinger of fouled water has brought with him the rivers of Styx, which he's used to establish a foothold in a region of space in the Vast.
The Pallid Princess, Urgathoa, maintains her divine domain within Abaddon. Here, she protects the shades who seek their afterlife in her service while also courting powerful undead who seek her direct counsel.