In many ways, Dolurrh is a machine. The pull that draws spirits to Dolurrh is a mechanical effect, part of the fundamental nature of souls. The denizens of Dolurrh are the cogs of that machine, here to keep the system running.
The Quick
The native creatures of Dolurrh are bound to the cycle of transition, and all have some role to serve in this process. All of the Quick are immune to the ennui condition.
Nalfeshnee demons patrol the Catacombs of Dolurrh, dispersing melds and lemures and dealing with mortal intruders. They appear as large humanoids whose features are shrouded in gray mist, and they delight in crushing mortals and pulling the shades from their corpses, as well as consuming lemures
Marut inevitables are powerful guardians, crafted in the Crucible of Dolurrh, forged from husksteel, and tasked to preserve the cycle of life and death. Maruts are occasionally dispatched to Eberron to intervene with acts of resurrection, or when a lich or mummy is created. No one’s sure what triggers this deadly intervention—perhaps the resurrection defied the Prophecy—but Jorasco healers always cast augury before raising the dead. If the result is “woe,” they refuse the job, lest a Dolurrhi marut appear, destroying the resurrected creature, its healer, and possibly the whole healing house in the process.
Shadar-kai are servants of the Queen of the Dead, shades granted new life. Though their new forms appear elf-like, they might’ve been any sort of humanoid in their previous life; when they caught the Queen’s attention, she preserved their soul from entrapment. The shadar-kai serve in the Vault of Memories, and occasionally as her hands on Eberron. They might clash with necromancers (especially the agents of Lady Illmarrow), collect trinkets, or target mortals with no rhyme or reason. Many sages attempt to explain these enigmatic actions, often speculating that they’re collecting especially tragic memories for the Vault. Other denizens of Dolurrh are unique, such as the Librarian, found in the Vault of Memories, and the Smith of Souls, who dwells in the Crucible.
The Dead
The spirits of those who have died are omnipresent in Dolurrh, from shades huddled in the shadows to layers of moaning mist. The Dead might be considered manifestations of Dolurrh, but the plane didn’t actually create them—all were once mortals.
Shades are mortal souls that are freshly arrived in Dolurrh. They maintain a portion of their memory and original appearance, though they’re insubstantial and can’t interact with material objects. Shades are susceptible to ennui, and as they gain levels, their appearance blurs and their memories slowly fade. Shades can speak, and they may cry or beg adventurers to help them; however, most are incapable of taking any actions on their own. They’re often found lost in thought, trying to remember something they’ve forgotten, or fixating on a past mistake.
Husks are harmless shades that have been overcome by ennui and possess only the vaguest memories of their mortal existence. Most retain a semblance of their mortal shape, but they continue to fade over decades, eventually merging with other husks to form masses of moaning mist. Having no true consciousness of their own, husks are immune to ennui’s effects. Occasionally, a group of husks cluster around a strong memory, forming an ectoplasmic mass that prowls in search of more scraps of memory, absorbing other husks. Such a creature is called a meld, and its statistics are provided in chapter 8.
Ghosts are formed when a shade clings to a particular memory with such intensity that even Dolurrh can’t completely eradicate it—perhaps a terrible mistake or a bitter grudge. The rest of the spirit’s memories fade, and it becomes immune to ennui, but this ember remains, defining its existence. Ghosts are driven by a primal desire to return to Eberron, to haunt the place where they died or where their anchoring memory was forged; they might escape to the Material Plane when Dolurrh is coterminous or when a resurrection goes wrong. Ghosts that are destroyed eventually reform; they can only find peace if their unfinished business is resolved.
Other forms of undead are rarely seen in Dolurrh. The entities found in this plane are the spirits of the dead, slowly fading, transitioning—or trapped in that process. Corporeal undead such as ghouls, skeletons, and zombies have no place here, while undead that hunger to consume life belong in Mabar.
The Lingering
Memories of joy and happiness do no harm in Dolurrh. But memories of pain, of cruelty, of anger . . . these don’t fade so easily, and they can hurt others. Even if they don’t trap shades as ghosts, this psychic residue can build up in the gears of the spiritual machinery of Dolurrh. It often takes the presence of a mortal to trigger it; when this occurs, the lingering pain and hate coalesces into a solid form. The least of these are lemures, formed from hateful memories or deeds. The emotional residue of hundreds or thousands of people can form deadly sorrowsworn—the Angry, the Hungry, the Lonely, the Lost, and the Wretched—as presented in Mordenkainen’s Tome of Foes. The Lingering are formed in Dolurrh and are immune to ennui, but they’re a waste product, not the plane’s desired result. As such, nalfeshnee, maruts, and other guardians destroy the Lingering whenever they are found.
Source: Exploring Eberron Chapter 5
A meld is formed from the faded souls of mortals—husks whose memories have been consumed by Dolurrh. These husks are typically harmless, but sometimes an aggressive nucleus gathers other husks, forming a deadly gestalt. In essence, a meld is a fusion of half-formed ghosts; it has an amorphous shape, with vague faces and limbs projecting from the mass, then being consumed once more. It makes no sound when it moves, but mortals around a meld hear cries of pain, pleading voices, and unearthly moans. Its Conflicted Soul action reflects it projecting some of its husks into a mortal body, temporarily overwhelming the victim with conflicting desires and visions.
Denizens of Dolurrh. Melds are born in Dolurrh, and prowl the endless caverns searching for scraps of memory. This hunger can draw them to Eberron through manifest zones or when planes are coterminous. A meld can also manifest when someone is raised from the dead, following in the wake of the soul being drawn back to the world of the living. Melds that enter Eberron rarely stray more than one mile from the point where they arrived.
Hunger for Memory. A meld has the barest traces of dozens of souls. It remembers scraps of the most powerful moments of its component husks, but it can’t place these in any context. The meld yearns to consume other spirits, to feast on their memories and emotions. While highly unusual, it’s possible for a powerful personality within a meld to exert temporary control; this might cause the meld to pursue a particular individual or draw it to a specific location. When a meld kills a living creature and consumes its spirit, the flood of memories can also shift the purpose of the meld, as it suddenly acts on the desires of its most recent victim. A meld loose in Eberron retains the spirits it consumes, preventing them from transitioning to Dolurrh. This prevents the spirit from fading; a character could hear the whispers of a trapped spirit within a meld, and a husk could hold the souls of people who died long ago. A side effect of this is that creatures slain by a meld cannot be resurrected or raised from the dead until the meld is destroyed.
Undead Nature. A meld doesn’t require air, food, drink, or sleep.
Source: Exploring Eberron Chapter 8
Nalfeshnee (demon), lemure (devil), marut (inevitable).
Monster Manual III: Sorrowsworn (demon), ephemeral swarm, plague brush.