Thanatos

Orcus, the fat-bellied ram-headed Prince of Undeath, is one of the most powerful demons in the Abyss. Even some of the plane's deities hesitate in fear upon the briefest mention of his name, for Orcus is more than just a demon. He is a legend that grows stronger and stronger with each revolution of the Great Wheel.

Orcus began life thousands of years ago as a wicked mortal whose vile deeds eventually resulted in his death. Thereafter his soul manifested upon the Abyss as a larva, then a mane. In that form he toiled long centuries under the lashes of now-forgotten demon lords, eventually managing through sheer will to evolve into a rutterkin. The Demonomicon of Iggwilv suggests that Orcus next became a nalfeshnee, and that he sat upon the 400th layer's Court of Woe during the era of the githyanki revolt against the illithid empire. Eventually, Orcus conquered the 113th layer and became a demon lord with the appearance he retains to this day.

Thanatos, the 113th Layer of the Abyss, is a frigid and frozen layer infested with the undead.  Several cities dot the layer (most of them ruled by minions of Orcus, including a powerful Succubus and Quah-Nomag himself).  Orcus rules from his palace of Everlost in the bone-meal desert of Oblivion's End, north of a vast mountain chain called the Final Hills that cut across the layer.  Despite Orcus regaining control over Thanatos, Kiaransalee's taint can still be found in the city of Naratyr on the Frozen Sea to the south of the layer, and in the so-called Forbidden Citadel in the city of Lachrymosa, located in the Final Hills.

Ash-gray clouds fill the cold black skies of Thanatos, the Belly of Death, where daylight never intrudes. The layer's immense, melancholic moon changes phases at random when covered by clouds, making time difficult to measure. A handful of cities crouch upon the layer's vast tundras, havens for the mortal and immortal cultists who seek to emulate the life of their demonic patron. Outside the cities, roving hordes of thousands of undead roam across the land in search of flesh. The strongest and most ambitious of Orcus's thralls attempt to dominate and command these armies, leading them on invasions of the Material Plane and the layers of rival demon princes like Graz'zt and Demogorgon.

Due to the layer's minor negative-dominant trait, all living mortals on Thanatos take 1d6 points of damage per round. Death ward and similar spells negate the damage for their duration. Mortal creatures that die upon Thanatos rise as undead (usually zombies) 1 hour after their death. Chaotic evil mortals sometimes instead become manes, dretches, or rutterkin. This process can be halted by raise dead or limited wish and can be reversed by resurrection, shapechange, miracle, or wish. Undead on the layer receive fast healing 3.

Because of the thin air, all living creatures must succeed on a DC 18 Fortitude save each hour to resist becoming fatigued. Fatigued characters must succeed on the same save or become exhausted. Characters who become exhausted on Thanatos immediately begin to suffocate.

Very little plant life exists on Thanatos. Mortals wishing to find sustenance must rely upon the indigenous mosses, molds, and fungi, and even these grow only in relatively temperate locales like Lachrymosa or Orcusgate.

Good-aligned visitors stand little chance of survival on Thanatos without the assistance of the Dustmen, members of a shattered faction who manage to eke out a grim existence here after being exiled from the city of Sigil on the Outlands. The remnants of the faction house themselves in the otherwise abandoned city of Vadrian, but generally have an outpost in all of the cities of Thanatos. The Dustmen know the layer well and offer their services as guides for the right price. For some reason, the native undead usually ignore anyone accompanied by a member of the faction. Not so the mortal Skull Lords and the immortal fiends, who often seek out parties led by Dustmen guides lest anyone get the impression that it is easy to survive in the Abyss.

Denizens