The Athasian Underdark

The earlier thread on the Night Below made me realize that the idea of a subterranean realm in Athas is something that’s probably come up on more than one occasion. So I thought I’d start a thread inquiring as to what thoughts people might have on the Athasian Underdark. If it would exist at all, how scarce the resources would be compared to the Forgotten Realms Underdark (the poster child for an underdark absolutely teeming with life), as well as what kinds of creatures would be appropriate for such a realm.

To kick off the thread I was going to start with my own rough notes on what I detailed for my own (very) homebrewed take on Athas.

"Chthonia is a strange realm of nightmares hidden beneath the burnt world of Athas. Although vast underground caverns have existed in Athas since time immemorial, Chthonia or the Chthonic Regions as we know them could never have come to existence without the interference of intelligent races. The core tunnels and caverns of Chthonia were first established by the Rhulisti during the crisis spawned by the brown tide. Seeking to escape the devastation the brown tide brought the Rhulisti established vast underground realms where the brown tide could not follow.
They used their life shaping talents to make the largest and most desirable caverns inhabitable for entire cities. The Rhulisti would go on to spread life throughout the underground caverns and tunnels, creating new and diverse fungus life that they could farm with relative ease, as well as hardy beasts that could survive underground without difficulty. A new ecosystem was blooming underground and the diminishment of the brown tide and construction of the Pristine Tower only magnified this flowering of new life. The Rhulisti took pains to connect their underground realms where they could, carving and expanding tunnels throughout the bones of Athas with the aid of fantastically crafted life shaped burrowers that are said to live in the Chthonic Regions to this day.
Eventually however the Rhulisti would fade from their underground realms, either seeking greener pastures above in the now flowering world or being driven out by new creatures that had come to call Chthonia home. It was in the Green Age when the Chthonic Regions would earn their name after all. The dwarves in their quest for greater riches would discover a harsh but strong ecosystem beneath their mines. They quickly realized the plants and beasts below could feed cities when properly cultivated and began establishing great stronghold cities inside the mountains of Athas.
As these communities began to thrive, humans too grew curious of the mysteries of the world beneath their feet and began various expeditions below the earth. However the insights of elves and men into the world below would prove paltry compared to the dwarvish achievements. The dwarven high king had his people build tunnels on an unheard of scale before or since that would connect all of their strongholds together. In time other races that inhabited the former Rhulisti cities would undergo similar projects on a far smaller scale. These dark paths represent the greater region of Cthonia that is heavily connected. However many large portions of Cthonia remain completely isolated to this day."

Chthonic Waters: Much of the water in Athas is buried underground, allowing for far more life to exist in Chthonia than one would ever imagine from a world as barren as Athas. Lakes and even a river or two actually exist in parts of Chthonia, however most water sources are unfortunately contaminated by minerals, making them undrinkable without proper filtration. However the fungus and animals nourished by the chthonic waters are another matter entirely.

Stygian Gates & Caverns: Aside from the dark paths, the chthonic regions have almost nothing keeping them connected to one another. Unlike the worlds of Toril or to a much lesser extent Oerth, portals are all but unheard of in Athas. However there is a strange anomaly within the chthonic regions that often connects them together, the so-called “Stygian Caverns”. These are underground caverns that exist in the gray, but not in the material plane, while others are sites where the gray and material plane bleed over completely. The openings to stygian caverns lead directly to the material plane and while some of these entrances and exits appear to be constantly active others require special activation through specific objects, spells, or phrases, making these so-called stygian gates very difficult to navigate. Creatures adapted to Chthonia have often learned how to open stygian gates naturally as well as survive in stygian caverns, either long enough to make it to another stygian gate or sometimes permanently survive in the stygian cavern if necessary. There are even known species of fungi that have spread to both the gray and the material plane, sharing a link with the two realms. Stories of stygian beasts that live as freely in the gray as they do in Chthonia are also whispered of.

Terrors of Chthonia

Caligni: Also known as Dark Men they are descended from refugees that fled underground to escape the Cleansing Wars. They made a deal with entities of The Black to allow them to survive underground. The creature of the black guided them to sources of food and water, yet the food and water the refugees consumed slowly changed them. Touched forever with the substance of the black the refugees would call themselves Caligni and under the direction of their false gods form a caste based society through which they would build thriving civilizations within the bones of Athas and observe the activities of the surface cities and their sorcerer kings.

Githyanki: Legends hold that the ancient progenitors of the Gith lived in fantastical gem studded cities below the earth. Supposedly these ancient Gith travelled to the moons of Athas and beyond in strange flying ships where they raided every realm they encountered as reavers, slavers, and mercenaries. What part they played in the Cleansing Wars is unknown, but no records of these ancient GIth exist after the Green Age. All that remains are their degenerate kindred and stories of their lost subterranean cities teeming with psionic treasures and the ancient moon gates of lost githyanki.

Morlocks: These strange humanoids appear to be massive devolved parodies of men with long apelike arms, flat noses, gleaming wideset eyes, shaggy pelts, and pointed teeth. They gladly devour any source of meat they can with a feral abandon that would give many thri-kreen pause. They shun daylight entirely and only emerge upon the surface of Athas at night where their shaggy hide protects them from the biting chill. Old legends claim that some towns sacrifice the lives of their own people in return for the morlock’s labor and protection.

Necropoli: Legends hold that entire civilsations of undead persist in the darkest corners of Cthonia, erected as grim parodies of the many legends of the afterlife. It is believed these necropoli are erected in or around the largest stygian caverns, where the grey overlaps completely with entire cthonic regions.

Neothelids: Within ancient cyclopean cities new and alien life slowly grows under the dominion of these wormlike horrors. Those unfortunate souls that are ensnared by a neothelid’s psionic at best can hope for their brain to be swiftly consumed. Otherwise they will be offered to the colony for ceremorphosis as a neothelid grub if inserted into the victim’s ear and they are slowly transformed into an illithid, the foul servants of the neothelid masters. Few psionic beings can match the neothelids and their illithid children in sheer psionic might and skill. Yet what foul agenda these terrible beings hold can only be guessed at.

Rhulisti: The oldest tunnels in Cthonia contain brightly colored walls as smooth as bone that lead to vast caverns teeming with fungi, running water, and strange round structures bristling with growths. What few accounts of these realms exist all attest to horrific monsters dwelling in these caverns that have never been seen anywhere else serving as primeval guardians of these lost lands.

Shardminds: On occasion explorers have encountered crystalline formations that ape the forms of men and beasts. Stranger still these crystals are potent psions and are capable of animating themselves entirely through their mastery of the Way. Little is known of their society, but they appear to be rather primitive and clannish.

Tari and Gith are both existing examples of races that would do just fine in Cthonia and I had a rough idea of Athasian Derro as a strange interbreed of gnomes and dwarves that were hiding from the cleansing wars. Additionally the idea that subterranian athasian trolls might have escaped the cleansing wars and became something very different is also quite appealing to me. However these ideas haven’t been fleshed out by me at all and I’m not sure if I’d even use them.


Excellent ideas! A question that has occurred to me over the years is why there were no subterranean communities detailed at all in the official setting. Seeing as the land was scorched beyond salvation, sorcerer-kings/queens hunted down races and dangerous creatures terrified the wastes outside the city-state walls, it would seem quite reasonable for some, if not many, to head underground.


The issue with an underdark type setting is that it removes a lot of the survival aspects of Dark Sun. For example: You are shaded all the time and underground is generally cooler than the surface. I mean what is Dark Sun without the sun? I would avoid adding trolls back into Dark Sun as well, because no trolls is one thing that makes Dark Sun unique.

That being said, the designers do hint at some sort of underground realm or realms, such as Under Tyr and Kemalok. I believe if vast underground realms did exist, they would be swarming with Dwarven Banshees, from the Dwarves killed by Borys.


I think that if I was going to do something underground it would be a few sessions and I would use the dwarven mines. I’d create a small micro climate generated in that a andoned mine. It could be super fun, full of banshees and twisted creatures.
Also for my taste it could be much to create an underground society in Athas. Don’t get my wrong, the underdark is one of my favorites setting, but I don’t see it fitting in Dark Sun.
Maybe I could use the idea of a hidden village close to the surface.
I also could do something deep in the sea of silt, creatures way more twisted than in dwarven mines. It could be a totally freak adventure, like floating in the astral sea, but you can’t see or breath normally. Creepy.


I think Meenlocks would fit perfectly!
Hook Horrors

I think these match pretty well too.
What do you think?

1 Like

I always thought Cynidecia (B4 - The Lost City) was begging to be ported to DS.

But also I agree that an Athasian Underdark would quickly start ro feel very non-DS.


Agree on both.

I always thought the same thing, in facts that’s the whole reason I got the module!

I haven’t added the underdark for that very reason. You’d have to figure out how to Dark Sun-ify it.

1 Like

The thing with an Athasian Underdark is it would focus on a lot of similar aspects of survival to the desert wastes themselves. If the forgotten realms underdark was just copy pasted straight into Athas then you would definitely have an environment that is in many ways more desirable to the surface of Athas.

The thing is though that just as resources are scarce on the surface of Athas so should they be below. Water and food should be just as rare in the Athasian underdark if not more so than on the surface. Life would likely concentrate around very specific areas where there is just enough water to sustain a small ecosystem, however that is no different from the oasis and villages you find on the surface of Athas.

Survival is just as bad underground if not more so. You’re not worried about the scorching sun but you trade that for the fact everything is more scarce. Food, water, oxygen, light, space, everything.

In my opinion when introducing other regions into dark sun it is vital to maintain the theme of the struggle for survival, but that doesn’t necessarily mean everything has to be a sun blasted waste. A polar region of hellish blizzards and primeval behemoths stresses that theme just as effectively as the tablelands and the effects of defiling would see the vegetation there diminish but the chill would persist, perhaps even worse with no woods to offer respite.
(I’ve actually heard a rumor dark sun was meant to be set in an ice age style environment but in the end it was set as a desert based setting for the sake of fetish armor. No idea how true that is, but I’ve heard it from multiple folks.)

1 Like

That’s fair. I think I remember a comment by Drizzt in some (maybe the Dark Elf trilogy) book about how awful, barren, lifeless, brutal and hard to survive in the Underdark was; but he was happy to live & die free. Sounds pretty DS to me.

My plan was to apply the 8 Characteristics of Athas to B4 and see how it looks…


I would include the remnants of a race that (barely) scaped the Cleansing Wars by going underground.


Yes, porting it straight over would be awful.

I do see your point. It would require a lot of thought and planning to do it right. For example, if water is as scarce underground as above, things like fungus and mushrooms would not grow. Those are probably major food souces for underground creatures. So, they might have to turn to raiding the surface world to survive.

Also, a lot of undead. So many it makes Ravenloft look lively by comparison.


The Rhulisti connected cities via underground tunnels. The underdark may just be a large tunnel network, overrun with lifeshaped creatures that will now consume anything they can find. Think of an organic cleaner that will eat anything it comes across…

Put in a few non-connected areas like under Black Spine and you have some living type areas, mostly isolated, but a few that connected to the tunnels, were then overrun by the lifeshaped creations.

You can also have an underdark type area using the Abashai I think they were, from Sandstorm. Adapt them for the sea of silt and they could have small cities and tunnels all over the place, nobody would know about them, and basically nobody could live in them either (except the Abashai).


I always liked throwing Underdark creatures into the tunnel system presented in City by the Silt Sea, mainly because i had a group that wanted to use them as a means to reach islands in the Silt Sea. Mummified aboleths proved to be quite effective at curbing player-interest in reaching those islands. Also always liked the idea of Athas being the birthplace of illithids, though I’ve never used them in a DS campaign.

1 Like

Not so great at writing out everything as some above but, basically I have a almost endless world of twisty and turning tunnels covering the underneath of Athas as my take on it

There are multiple “hub” areas where underground cities or villages for a lack of better term have collected. I currently have 4 sentient races that inhabit the underneath, the Myconids who are a fungi race, the Quaagoth who are a take on Chitin covered Yeti-Like people, and the Cysilinoids which are a race of Psionic crystal people, and last but not least I have the Gensai which are descendants of the elementals and the influence they have on the world.

The three main factions, Myconids, Quaagoth, and Cysilinoids, all control different areas of the underneath and are in tense peaceful relations with each other, though each group has its own bad apples that get exiled to the endless tunnels or put to death. The Gensai live within all the areas, with no lands they call their own, and in my Athas the Gensai are all one race and when they are born they are “randomly” given the heritage of one of the elements, so Gensai of two different elements are still considered the same race, and when they mate could have a child of any of the 4 main elements.

The Underneath and the Surface of Athas have no idea about each other, each just existing on its own. Both are hostile, with very limited resources, and filled with monstrous creatures that have adapted to live in their particular environment.

Thats my take on it, I try to make it something vastly different from the surface, but I keep the main themes I believe Dark Sun should have such as the survival in an unknown and hostile environment. I also wanted to stay away from the usual theme of the underground being filled with Undead, Dark themed versions of the standard races, and troupes such as that.

There is life below, just a very different variety of it, and it is also just fighting to survive. If my players ever get to it, they may just find that there are links to the Primordials in the Underneath and who knows what could happen then.

1 Like

Honestly, I was under the impression that the Underdark was just populated with undead giants and Dray. I got that impression from Dregoth Ascending.

1 Like

This is a topic that’s always interested me. I think the subterranean portion of athas would have been purged of life during the cleansing wars. Possibly by gas, or something that could satisfy the champions that no one would escape the cleansing, by hiding in an underground cave accessed via a flooded tunnel.

I believe there are pockets of life, underground, but they’re incredibly rare, and each would probably be unique. I wish I had my old notes, since I can’t remember much, but I believe giant worms infest the underground, along with other large creatures. Lots of silt, and fouled water. Possibly many places were sealed by lava.

I also think the underground would have been trapped, killing victims of the cleansing. Probably not the whole underground, but enough to make a difference, and to make most of the underground unfit for the living, which would help explain why society doesn’t live in an underground psionic paradise. I mean, dwarves did it with chisels and hammers, and maybe a rock eating worm or two. :beer::dash: