Castoffs, prisoners, rejects, the lost and forgotten, all those adrift in the multiverse have a tendency of winding up in the Tartarean Depths of Carceri. Like a magnet, this inhospitable plane draws these discarded elements towards its torturous depths and keeps them there. A subtly powerful force keeps Carceri's planar gates and portals shut, with a few notable exceptions, and travelers are warned that finding a way into one of its layers is far easier than finding a way out.

Carceri's reputation as the prison of the planes is well deserved. Some say it was a union of gods from across the multiverse that created the prison plane. Though for whom originally has long been forgotten. Carceri is a plane of subtle evil that saps the strength away from those who visit. A slumbering malevolence pervades its infinite string of six layers as manifested by a red glow inherent in the ground and air.

The Tartarian Depths are also laid out unlike any other plane. Each of its layers sit as strings of huge spheres in an air-filled void. The layers are nestled within one another, spheres within spheres, with the space between each successive sphere in its line growing farther and farther apart. The exception is Agathys, which exists as a sole orb in the dead center of Carceri.

The layers are not uninhabited. A species of fiends called demodands, also known as gehreleths, operate as the wardens of Carceri, and always assume anyone they come across has good reason to be locked away forever. They are cruel embodiments of Carceri’s truest idiom – betrayal is the only path to freedom.

While Carceri exudes a scarlet evil, its existence as the prison of the planes serves everyone, from the fiends to the angels and everyone in between. Gods have birthed horrors beyond count that defy extermination, and Carceri provides the perfect dumping ground for the things that cannot simply be destroyed. Dark and terrible things fester within the multitude of orbs that make up Carceri, and many of them have birthplaces in the most revered places in the multiverse.

Getting There

There are many gates and portals leading into the layers of Carceri. The most numerous lead to the top layer, Othrys, but external portals from across the multiverse can lead to any of the first five layers of the Tartarean Depths. The exception is Agathys, which is accessible by no known gate within or outside Carceri.

Most gates into Carceri are known and well-documented by nearby inhabitants, and they can be found across nearly all of the Planes. Angels and devas watch over just as many Carceri portals as demons and devils; the Tartarean Depths are imprisoning for all creatures regardless of origin.

While many portals lead into Carceri, the opposite is not true. Finding a way out of the prison plane is difficult, and for some, like Cronus and the fallen titans, escape is divinely forbidden. Some residents have divine marks on them, preventing them from leaving, but even for those without such restriction, finding a portal leading out is a difficult and painstaking process.

One of the few exceptions to this is the River Styx, which winds through most of the swamp-filled orbs of Othrys. Its oily black waters slither like a massive snake through the red-tinged darkness of Othrys. The natural mind-altering properties of the River Styx prevent most creatures from even attempting to use it as a means of escape.

Traveling Around

Each layer of Carceri consists of strings of orbs in an endless chain, with the exception of Agathys, the lowest layer. Traveling between the orbs requires flight, but the endless darkness beyond is not a void, and creatures can breathe in it without difficulty. There is no gravity beyond about 500 feet from the surface of each orb, which means there is very little blackness separating the orbs of Othrys.

The swamp-filled top layer has its orbs closest in proximity, and from one a creature can view the next two in line from the right vantage point. The lower layers have larger gulfs separating them, requiring longer travel time in the darkness. Monsters do lurk in the darkness, most notably the strength-hunting sky shadows.

Accessing each layer from within Carceri can be tricky. Very few known gates exist that allow access to an upper layer from farther within the plane. Moving to a lower layer is much more straightforward, and numerous swirling portals of darkness exist on the orbs to the next lowest layer.

Theoretically, each layer's orbs are smaller, but some planar scholars believe this is a trick of the mortal mind trying to capture the idea of how Carceri is laid out. There are many monstrous threats on each of Carceri’s layers, but threading through them all are the malevolent demodands. Cruel, merciless, and wicked, these creatures were banished to Carceri long ago and now consider themselves the jailers of the whole prison plane. Truthfully, they hold little power over Carceri, and their natural untrustworthy nature prevents demodands from organizing in any large number.

Lay of the Land

Carceri is unique among the planes for many reasons, the most obvious of which is its landscape. The plane is divided into six layers, each consisting of strings of orbs in an air-filled darkness. The layers are nested within one another, with each lower layer filled with smaller-sized orbs but all contained in the infinite blackness.

As far as anyone has been able to surmise, the number of orbs in each layer is infinite, except for the lowest, Agathys. There is only a singular Agathys orb, and accessing it is a feat of incredibly dedicated proportions.

Othrys

The first and largest layer of Carceri is Othrys. Each orb in this infinite string is dominated by a dismal, scarlet swamp dotted by fetid bogs, stagnant lakes, and great swaths of dangerous quicksand. Desolate, lifeless trees stand like silent watchers in the gloomy twilight that pervades all of Carceri, their branches twisting together to form massive web-like growths that sometimes stretch out over many miles.

The orbs in the Othrys string are close enough to be separated only by 500 feet of darkness, though the lightless nature of Carceri makes even the nearest sphere nearly invisible from one to the next. There are several known exceptions, most notably Mount Othrys, a single solitary mountain peak rising from the fetid bog that connects two orbs together. Here is where the fallen titan lord Cronus makes his home amidst a complex swarm of lightning storms and driving wind.

The River Styx winds through all of the Othrys orbs.

Mount Othrys

The first slope of Mount Othrys rises up from a jumble of boulders within a dismal swamp on an orb in Carceri's first layer. It stretches up into the black gulf to touch a neighboring peak on the adjacent orb, and the two mountains form the whole of Mount Othrys, the mountain with two peaks. This is the home of Cronus, the greatest of the fallen titans, and his foul mood creates a perpetual storm of gloom and fierce red lightning around the entire region.

The few beings that have come to Mount Othrys have been invited by Cronus for various reasons. The mountain slope is treacherous and steep, but inside is a honeycomb of tunnels and rough stairs that serve as Cronus' personal lair. The point where the two mountains rise up and touch is the throne room of the fallen titan, a grand if gloomy chamber where Cronus sits and broods for most of his days. No other fallen titans dwell within Mount Othrys, but Cronus is attended to by various ogres, trolls, and other foul-minded creatures that serve the great titan with a zealous fervor.

There are rumors of treasure vaults inside Mount Othrys where Cronus has hidden away the great magical artifacts of his previous days on Arborea. The banishment curse that keeps him and his fellow titans on Carceri prevents Cronus from using these items, so he and his home have become unwilling guardians of these great treasures. However, Cronus has been known to bargain with outsiders occasionally, always seeking a means of permanent escape, and has used several of these powerful items as potential rewards. Most planar scholars believe that none of the treasured items have been released from Mount Othrys to date, especially considering that Cronus still remains imprisoned on Carceri.

Cronus and the Fallen Titans

No beings on Carceri more embody the prisoner mentality than perhaps the plane’s most famous inhabitants, Cronus and the fallen titans. It is widely accepted that these powerful beings hail originally from the storm-enshrouded peak of Mount Olympus in the Olympian Glades of Arborea, a fact the titans do not dispute. However, planar sages debate wildly the nature of the treachery that sent Cronus and his fellow titans on a one-way trip to Carceri’s depths.

Regardless of the origin of their crimes, the fallen titans have not been able to escape Carceri's grasp in any meaningful way. Over the centuries, many have tried, putting elaborate plans and plots into motion meant to release them from their planar prison, but to date, none have succeeded permanently. Cronus himself, the once powerful leader of the Titans, now sits alone on Mount Othrys, the tallest peak on the orbs of Carceri's first layer, and constantly schemes for release. His moods are foul, his anger earth-shaking, and his paranoia rampant. Cronus blames every other being in the multiverse except himself for his lonely fate.

The other fallen titans are spread across the layers of Carceri, living in isolation or small groups, never fully trusting one another or any other creature they come across. One fallen titan dwells in a crumbling castle in the scarlet jungles of Cathrys, while another pair crew a literal skeleton crew on the icy shallows of Porphatys. They are each powerful beings with great command over their abilities, all of which they bend towards the ultimate goal of freedom from Carceri's bonds. They are distrustful, but few in the Tartarian Depths know more about what’s happening across the orbs than the titans, who have seen eons pass. Even the demodands avoid tangling with Cronus and his fallen kin, preferring the easier pickings of lost travelers and lone prisoners instead.

Cathrys

Carceri’s second layer is Cathrys, home to vast swaths of dense crimson jungles and fields of scarlet grass. An acidic rot fills Cathrys’ air, eating away at organic matter. The scarlet grasslands move without breeze or wind, and most contain razor-sharp grasses that hunger for nourishing blood.

Smaller than Othrys, the distance between the Cathrys orbs in its infinite string is about 1,000 feet. Most of the fetid jungles of the layer seek out any that try to escape its grasp, pulling them down with a savage fury, as if Carceri itself sought to prevent travel from one sphere to the next.

Blood Orchid Vale

The jungles of Cathrys are dangerous to say the least, but truly some wonderous sight lay hidden behind the acid rot of the scarlet domain. Blood Orchid Vale is one such place, nestled in a low mountain range and filled with enormous flowers that give the area its name. It is also home to the dryad queen Thymea, who tends the valley with a host of servants.

Thymea is a prisoner of Cathrys but was once a powerful guardian of Arborea. She pushed against the advances of Olympus long ago, believing the trees and woodlands of the plane deserved more respect than the gods granted, and for her transgression, Thymea was cast into Carceri. She ended up on Cathrys and, through careful administration, built a new home for herself and her minions, but the treacherous nature of the plane wormed its way into her mind. What was once a noble defender of the forested realms has become an isolated, bitter creature determined to punish anyone who sets foot in her sacred valley.

Thymea is jealous and has twisted the natural vegetation of the valley to her isolated whims. Trespassers have faced black-barked treants, twisted blights, and blood-hungry shambling mounds. Trespassers are not uncommon since rumors of the fabled blood orchids that grow there have spread. Some say they have mystical healing properties and can even restore life to the dead, while others claim the sweet nectar can be distilled into a particularly potent poison. Sinmaker, the glabrezu demon that runs the Apothecary of Sin, has a standing bounty for anyone who can return a blood orchid flower to him, but to date, none have succeeded.

Garden of Malice

Most of Cathrys is wild, overgrown scarlet jungle and vast plains of red-tinged grass. Like much of Carceri, it gives the impression of an untended wilderness, but for travelers who stumble upon the Garden of Malice, that wildness is replaced by order and well-maintained flora amidst blooming flowers of all kinds. It is not a peaceful region, however, as great tigers dripping acid from their fangs stalk the paths and manicured bushes, all under the guidance of the garden’s master, the imprisoned Rakshasa Rameyos.

Rameyos is as cruel and manipulative as all of his kind, and he angered the wrong devil lord in a risky gambit in the past. That misstep sentenced him to a lifetime in Carceri, where Rameyos has decided to make the most out of his situation. The rakshasa always possessed a surprising affinity for plants, so he took an instant liking to Cathrys. Over the years, he carved out the Garden of Malice from the surrounding wilderness, bending the very land to his whim, and he learned to speak with the savage tiger-like monsters that stalked the scarlet jungle. Eventually, Rameyos' sanctuary flourished under his patient guidance and pruning, and in that time, he learned much about the special plants that grow only on Cathrys.

Rameyos is still keen to escape Carceri, but for now, he has contented himself with growing specialty plants for the poisoner Sinmaker in the Apothecary of Sin. The two exiled fiends have formed a partnership, with Rameyos supplying the raw ingredients for many potent poisons, and Sinmaker giving the rakshasa first refusal rights on the magical items given in trade for the demon’s lethal concoctions.

Minethys

A great scarlet desert fills the orbs of Minethys, Carceri’s third layer. Like the other layers, no wind blows that can be felt, but the sands of Minethys shift and move just the same. A parching heat holds dominance over the red sands, which hide more than one ruined castle or treasure vault. Some planar scholars say the great edifices and palaces of the titans banished to Carceri so long ago were cast into Minethys, though there are certainly some smaller sized sites that have been discovered that suggest it’s not just titan architecture buried in the scarlet sands.

The orbs of Minethys are separated by half a mile of darkness. The scorching desert heat exuding from the very core of each orb grows more intense as a traveler leaves the surface, draining life and energy away, until after about 500 feet when the heat barrier breaks and the encompassing darkness washes over.

Illmoor, City of Pillars

The red sands of Minethys move and shift with an almost primordial intelligence, all to the whims of no discernible weather or effect. They create sandwaves out of nothing, burying and revealing secrets on the countless orbs that span the layer.

Centuries ago, the great blue dragon Chaydarren stumbled upon a series of buried pillars rising from the newly uncovered scarlet sand pit. Curious, and with nothing else pressing, considering his imprisonment in Carceri, Chaydarren investigated, finding the lost remains of Illmoor, City of Pillars.

Since then, the blue dragon has become obsessed with unlocking the secrets of Illmoor. The city itself boasted hundreds upon hundreds of magnificent pillars, each carved with intricate sigils and runes of arcane mystery. Chaydarren has been able to translate some of them, and in the process, he has learned that the city boasted a magical academy that lifted the citizens to profound heights of opulence and wonder. What Illmoor did to become cast into the red sands of Minethys is still unknown, but Chaydarren has already learned many new and powerful magical secrets to make him a force to be reckoned with.

The blue dragon is not the only one interested in the ruins of Illmoor. All around the site, black-bandaged mummies rise up from the scarlet sands to fight against any who tread the city's ancient pavilions and causeways. Chaydarren believes these to be Illmoor's original inhabitants, cursed to protect the city against all invaders by the same power that banished them all to Carceri, and the undead have proved to be quite a nuisance. Chaydarren has come to believe these dark guardians are under the guidance of some larger intelligence, as they move with surprising tactics and always seem to know where the blue dragon is going to be working next.

Word of Illmoor’s discovery is beginning to leak out across the multiverse, and Chaydarren has spotted several expeditions of adventurers and arcanists in recent years. Most of those fall prey to the black-robed mummies, but the blue dragon has personally had to deal with a few. Illmoor’s secrets are Chaydarren’s to unlock and hold, and he jealously guards the site against any he views as invaders.

Sand Tombs of Payratheon

One of the better known secrets of Minethys is the remnants of Payratheon, a site filled with tombs and sarcophagi buried beneath the scarlet sands. Treasure hunters and adventure seekers have found that the shifting sands of Minethys only reveal Payratheon for about an hour at a time, but in that time, great relics have been found interred with the dead.

Unfortunately, treasure is not the only thing to be found in the sand tombs of Payratheon. Monstrously powerful creatures that resemble gorgons perpetually stalk the dunes around the site. No one knows if these are intentional guardians or just opportunistic predators, but the result is the same. They chase down visitors to the area and seem to especially enjoy surprising foes that have burrowed into the sandy waste in search of Payratheon’s secrets before the shifting sands reveal them naturally.

Some of the items found in the sand tombs suggest the area is the final resting place of a great religion dedicated to a long-lost god. Magical scarabs and unusually curved blades have all been pulled from Payratheon, but more than a few seem to bear an unusual curse on their bearers. At least one adventurer had their body liquified from the inside by a boiling black ooze after claiming a gem-encrusted scarab ornament as their own, and several others have been haunted by visions of jackal-headed demons in the night before relinquishing their claim on uncovered treasure.

Colothys

Jagged red mountain peaks scour the landscape of Colothys, the fourth layer of Carceri. Deep ravines, shadow-filled crevasses, and scarlet-mist enshrouded valleys fill the endless orbs. Travel is nearly impossible outside of little-used trails that move along rickety bridges and crumbling stone stairs. Noises and sounds are amplified a hundred fold in the haunted mountains of Colothys, with some screams bridging the gap between the orbs to echo weirdly against the scarlet stones.

Colothys’ orbs are separated by mile-long stretches of darkness that are filled with screams, cries, wails, and other tortured sounds. It is rumored the darkness holds the Sepulcher of Screams, the resting place of a banshee queen cursed to wail forever in the emptiness of Colothys’ space.

Canyon of the Carrion King

In a particularly deep crevasse on Colothys, Carceri's mountaneous orb layer, the screeches of vultures and crows echo for hundreds of miles. Here, in the Canyon of the Carrion King, the scavengers pick flesh from bones and hunt for fresh meat to satiate their master's inestimable appetite. The Carrion King is an enormous, grossly obese vrock that hides in the shadows of its canyon, sending out minions to do its bidding and searching for a way out of Carceri.

The Carrion King was an agent of Demogorgon in the Abyss, serving faithfully in the Blood War, when a chance opportunity arose for the ambitious vrock to usurp a more powerful rival. The plan went awry, however, and the favored rival pleaded with Demogorgon to treat the vrock as harshly as possible. Death was too quick an escape, so the demon lord cast it into Carceri to live until it grew strong enough to fly out of the prison plane. Now calling itself the Carrion King, the vrock decided the only way to grow strong enough was to grow as large as possible.

It cajoled and magically enchanted the monsters of Colothys to do its bidding, and eventually it attracted the attention of the hatemonger vultures that wing through Carceri’s darkened skies. The monsters fell under the Carrion King’s sway almost instantly, and soon the vrock began to gorge itself on the offered feast. Its wings grew strong and large, and it tried to fly out several times, but the pull of the prison plane kept it from escaping. So the Carrion King dug deep into its canyon and commanded its minions to keep bringing it food.

Now, the Carrion King is likely too large to fly or escape its canyon without great difficulty. However, the prize of escape remains the light that keeps the engorged rock going on its path of gluttonous glory.

Porphatys

The orbs of Porphatys are covered in an icy shallow sea, less than 100 feet deep in most places, while crimson snow fills the darkened skies. Prison ships filled with pirates and thieves cursed to sail eternally bob amidst the icy black waters, sometimes running aground on one of the countless sandbars. The water is mildly acidic but eats away at inorganic matter quicker than organic matter. Eventually, every ship on Prophatys’ sea collapses, stranding prisoners on shrinking islands, crumbling towers, and other unstable regions, promising treasure to any willing to pick them up but rewarding only such kindness with eventual betrayal.

The orbs of Porphatys are separated by three miles of darkness. The red snow that fills the dark skies of each sphere stretches out into the space between them as well, though none know its source for sure.

Ship of One Hundred

The shallow seas of Porphatys, like the other layers of Carceri, hold secrets aplenty, many dangerous or lethal to the foolhardy. The mysterious vessel known as the Ship of One Hundred is one such secret. It is a massive, bonewhite ship without crew or sailors, yet it winds through the snow-laden seas of Porpathys with expert skill, avoiding sandbars, rocky islands, and other obstacles that may sink it or cause it to run aground.

The only cargo aboard this mysterious ship is one hundred stone sarcophagi in the lowest hold. They are unmarked, bearing no writings or sigils of any kind, but all who have opened one have met with a grisly fate by some unseen force aboard the vessel within an hour. Is the ship powered by the imprisoned souls within the sarcophagi? Or is it their prison as others have surmised? Like much of Carceri, divine guidance offers no insight into the truth behind the Ship of One Hundred.

However, that doesn’t mean the ship is uninhabited. The lost and forgotten that populate Porphatys have found that, as long as they leave the sarcophagi alone, they can move about the ship unmolested by spirits or evil forces. The ship never stops for long in any one location, and it can transport itself between the orbs through the summoning of a thick fog. Some residents of Porphatys have taken to living on the darkly mysterious ship, which seems to hold more room than a normal ship of its size would suggest.

Agathys

The lowest and smallest layer of Carceri is Agathys, and unlike the other five, a single orb serves as the only destination within the confines of its limitless darkness. Agathys is frozen solid, an icy sphere of black cut through with streaks of crimson like blood vessels. Anyone doomed to Agathys is frozen forever in its depths, and in many places on the surface of the orb, faces and bodies can be seen in the ice.

Little is known about Agathys. Some planar scholars say it is the actual frozen heart of Carceri, which does operate much like a living creature on a massive scale. Others say the ice is the result of some ancient power of death known as the Reaper, and certainly there is some evidence to suggest this is at least partially true. One of the few known sites on Agathys is the Citadel of the Reaper, a long tower with cavernous tendrils cut into the frozen ground, where death stalks the halls.

Citadel of the Reaper

The Citadel of the Reaper is the only structure known to exist on the surface of Agathys, the deep dark heart of Carceri. It is a black stone tower rising from a bowl-like depression on the frozen orb, and its walls are filled with the frozen faces of the dead. Those few brave explorers who have tread the darkened halls have heard the muttering of those frozen dead and experienced the cold shiver of wraith-like monsters that move silently in the shadows.

Most agree that this mysterious citadel was or is the home to a powerful deity of death and cold, but whatever master built it seems to pay little heed to it now. The deck of many things, known throughout the multiverse for its capricious nature, is the only known tie to the citadel. One of the cards summons a vestige of Death, and those killed by this specter are imprisoned forever in the walls of the Citadel of the Reaper.

Several black-hearted necromancers and other masters of the undead have sought out the Citadel of the Reaper in an effort to glean sorcerous secrets from its shadowhaunted halls. Rumors persist of a library within the citadel wherein hide necromantic arcane formulae lost to the multiverse.

The Reaper

Servants of the master, known only as the Reaper, wander its citadel and keep intruders out. They are black-robed, red-boned skeletons bearing scythes writhing with negative energy. They do not speak and make no noise, and in fact, the entire citadel has a death-like quiet about it. Thoughts become whispers, whispers become shouts, and it is said that the master of the citadel hears all that happens within the halls.

What is the Reaper? Some say it is a deity of death and ice who has chosen to dwell upon Agathys, while others say it is a being beyond the gods that commands a legion of undead monsters to do its bidding. The Reaper rarely sends out minions beyond the halls of the citadel.