Beneath the surface of the Earth, a menace and a cancer slowly worked its way outward. Like a worm hatching from a single egg into a great, winding thing that chokes its host, so did the Ch'thra work slowly to put their vile plan into action.

The musky smell of the beasts permeated the stuffy air within the close tunnel walls.

'Approach, faithful servant.' A low rumbling voice, inhuman in tone, issued from the far darkness. The speaker could be seen only as a large, undulating mass of uncertain shape in the dim lighting.

In this place, where there was naught but a slight reddish glow, a man stepped forward from darkness to lesser shadow.

'I am here, Oh Superior One.'

'You were successful?'

'Correct, your Magnificence. The best crop yet. I have twenty-three healthy..., well, mostly healthy... specimens. Five male, twelve female, six undetermined. All sex workers. All unaware they were taken. All ready to be processed.'

'Excellent. You are our best servant, human. You continue to earn your place among the living.'

'I live only so that I may serve.'

A chittering. 'Yes. You know your place. Bring them to me now.'

The man motioned and from a twist in the tunnel the first gurney was wheeled in, the girl upon it deep in slumber. Two grubs handled the gurney as well as they were able, using their bloated white bodies (reddish in the current glow) and stubby forelimbs to force the unfamiliar device forward.

The speaker detached itself from the deeper darkness, lumbering forward to hover grotesquely before the body, clasping and unclasping its various limbs in impatient glee. Its face leaned over that of the unconscious girl. Two minor appendages with grasping claws held her face in place while a third, smaller tentacle topped with a stinger moved near her neck. With a quick strike it was done. There would be no marks but that of a small, red, swelling dot, which would appear as no more than an insignificant spider bite. Beneath the surface, however, the disease was already beginning to take hold.

Progression of the Disease

After infection, the disease took more than three weeks to show any symptoms. By that time, the well-placed Ch'thra agents had managed to spread it to a significant number of vectors across several major cities. Being unaffected by the usual safety precautions, it spread quickly from the prostitutes to their johns, and through them to others.

Symptoms, once they did set in, seemed more akin to a moderate fever than anything else. The fever would appear to come and go for a week or two before fading away completely. From there another week of relative normalcy would occur. After that time, the victim's heart would suddenly stop. Death would be instantaneous. Within twenty-four hours, the victim would almost invariably arise as a mindless, ravenous zombie and an unwitting servant of the Ch'thra.

It was, therefore, more than six weeks between the first injection and the appearance of the first zombie. After that the disease spread faster than it could be accounted for. At first the death rate spiked. And then the world was too busy dealing with marauding corpses to pay attention to anything else.

The newly risen quickly spread the disease to others through blood contact, often by biting. The incubation period was less than half that of the original. Even once they knew what to look for, Earth's scientists could only scratch their collective heads in frustration and wonder as to the cause. A cure seemed far too far away to matter. Earth was dying. Many families watched their loved ones go through the transformation, completely helpless to do anything but contemplate the most drastic of actions.

Once civilization, and with it any form of coherent defense, had broken down, the Ch'thra emerged from their myriad tunnels beneath the earth. City by city they went, claiming the land as their own, calling forth their rotting zombie servants to attend them.

Only small, dwindling pockets of resistance exist.

The Ch'thra

The Ch'thra are a race of horrors who burrowed into the depths of the earth via an interdimensional rift from their own homeworld. They appear as a madness-inducing combination of insect, worm, and slime. And though they opened the rift by pure accident, they were quick to take advantage of it.

Ch'thra technology is primarily based on genetic manipulation and other biological wonders, mixed in with knowledge of a limited type of arcane sorcery. They are able to bind together these eldritch powers with their knowledge of biology to produce effects far beyond our own understanding.

This technology has been practiced on themselves as much as on others so that few Ch'thra look anything alike. Many have telepathic powers and are able to control those mentally weaker than themselves, criteria which includes all but a very minute portion of Earth's population. Zombies created by the Ch'thra can be controlled in this fashion.

Physical Description

Adult Ch'thra range in size from 10-15' in height, 12-18' in girth, and weigh many hundreds of pounds. They tend toward long, tubular bodies, and thus do not stand up straight. Rather, they trail their lower portions upon the ground and hold the rest of their bodies upright. From the joints in their segmented bodies pours a steady stream of thick mucous. A multitude of limbs protrude from their bodies at seemingly random points. Many of these have been added artificially. The limbs themselves vary in length, strength, and flexibility. Some may be used for propulsion while others for fine manipulation or tools of their sorcerous biotechnology. They are generally insect-like in their construction.

Outside of intentional genetic manipulation, five major natural subtypes of the Ch'thra exist:

  • Joth: The largest and meanest. Joth are the natural leaders who work through bullying and violent outbursts. Their faces are chitinous masks with multiple beaks and a hundred tiny eyes. Along both sides of their faces are an array of tentacle-like appendages which are a sign of their great mental abilities. They are capable of crushing the will of others by a touch of these tentacles.
  • Teth: Scientists, second only to the Joth and slightly above the Keth, Teth are as long as Joth but thinner in build. They have a dozen large bulbous eyes upon their faces and have the widest array of manipulators on their upper bodies. Fuzzy antennae rise from the tops of their heads, giving them an enhanced range of psychic perception. Teth are responsible for Ch'thra technological production and development.
  • Keth: The upper ranks of the military. While slightly smaller than Joth, Keth have a wide array of weapon-appendages. Their faces are similar to the Joth, though they lack the head tentacles.
  • Moth: Few and far between, Moth give birth to the grubs of the various subtypes and care for them until they can be passed off to the adolescents. All Ch'thra look the same at birth; they are the grubs which fill the lairs. Attrition rate is high amongst the young as they are encouraged to view each other as direct rivals.
  • Jeth: The grunts. Any work that cannot be passed off to a grub goes to a Jeth. Jeth are the smallest and most numerous of the Ch'thra. As such they are at the bottom of the pecking order in Ch'thra society.

Grubs do not differentiate into a particular subtype until they reach adulthood.


All Ch'thra technology is based upon biology and sorcery. Tools are grown and adapted. Just as on Earth, technological development occurred over millennia as more and more complex tools were formed from simpler ones. Plants and animals were bred for certain traits, guided later on by subtle sorceries, until they became mere stepping stones to more fine-grained manipulation.

Rock-eating worms were grown to chew through rock and create the tunnels, manipulative appendages were grown for performing grotesque surgeries, parasites were adapted to the nervous systems of other species in order to create Thralls, bacteria-infested slimes capable of transmitting desired genes to a host. All this and more focused toward the expansion of Ch'thra civilization.

Weapons tend toward dart-slinging organs or claw-tipped tentacles, both exuding whatever poison or some other substance of choice.

Discovery of the purpose of any Ch'thra device is fraught with danger. It is usually difficult to tell what triggers a particular item (in fact some are triggered by the proximity of humans or psychic suggestion) or what it will do without significant, and highly dangerous, experimentation.

The Tunnels

The first tunnel appeared in the Rocky Mountains not far from Denver. With sorcerously mutated beasts which were able to chew through and digest the hardest rock with ease, the Ch'thra were able to create a complex, twisting network of tunnels. The first few humans they encountered were quickly taken and studied. The young were found to be excellent fare while many adults were sent to the labs for study. Some humans were implanted with a parasite to make them faithful servants, the Thrall, agents of the Ch'thra who could be seen where the aliens could not.

Within a few years, the tunnels had spread to most major cities in North America. Single-shafted tunnels connected the twisting, roiling complexes that existed below the cities themselves. Most towns and smaller cities were ignored.

As the numbers of Ch'thra increased, some were shipped overseas by their Thralls, to begin tunneling under the cities of the rest of the world. After seven years, the Ch'thra were well established and the humans had been thoroughly studied. The plan was ready.


The layout of a Ch'thra lair is organic and without obvious patterns. The tunnels, being mostly round with a flattened floor, generally vary from three to ten feet in width. These tunnels rarely stay even, meandering up, down, sideways, and at all angles in between. Randomly placed hand and footholds allow easy passage for the large Ch'thra; for an average-sized human it can be a slow and frustrating affair.

The Ch'thra see only in the lower wavelengths, from orange down to low infrared, and thus have very little lighting. In any case, sight is not their primary sense, making them fierce enemies in the darkness.

Rooms are little more than bulges in the tunnels. Most are twelve to fifteen feet across. A few are as wide as thirty. Most fit into the following types:

  • Grub nursery: Dozens to hundreds of the bloated three-foot long creatures known as grubs pile together in the middle of the room. There are usually a few adolescent grubs present to see to the needs of their young.
  • Ch'thra dwelling: Most Ch'thra have their own dwellings. These are disgusting places, with rotting garbage (mostly leftovers) mixed in with a squirming array of living tools. Ch'thra sleep for fourteen hours each day but without any set schedule so any mission in the tunnels will involve making it past a number of the sleeping creatures.
  • Lab/workshop: These are the workspaces of the Ch'thra and tend to be somewhat indistinguishable from their dwellings.
  • Storage: These room can hold anything, from slime-coated, gelatinous food bags to squirmy tools and piles indistinguishable from rotting garbage.
  • Meeting hall: The Ch'thra mostly communicate telepathically with each other (making it difficult to infiltrate a lair without warning the entire complex) but they do occasionally meet in groups of a dozen or so. These tend to be the larger rooms but they are also the rarest. These rooms do double duty as dining halls.


The dimensional rift which connects the Ch'thra homeworld with Earth is still active. More Ch'thra pour through every day, many hopeful to escape a lowly station at home and to obtain their own cadre of human slaves, both dead and living.

The Zombies

Aside from a glazed look to their eyes, the freshly dead could pass for living in a crowd. Or, they could if they didn't feel the constant need to bite everyone. They are fast and strong and don't feel pain, acting as though under a constant flood of adrenaline. They cannot speak, but only because their brains are no longer capable of forming coherent thoughts.

As time goes on their bodies begin to decompose. The further along this process is, the slower and weaker they become. Since they do not feel pain, they tend not to notice, or be fearful of, broken or missing limbs. The only way to take a zombie down is by removing/destroying the head or destroying enough of the body that the zombie is no longer a threat (the head will continue to bite anything nearby until destroyed, however.)

There are several variations of zombies that appeared after the initial flood, when the Ch'thra were able to emerge from their tunnels and attack humans without subtlety.

  • Brutes: These are ogreish in size and appearance, with grotesquely enlarged muscles and skin thick enough to be leather. Calcified nodules dot their bodies, acting as additional armor. Many carry any large object that can be used as a club. In spite of their great size, they are just as fast as the regular zombies. A group of three or four Brutes should give pause to any party.
  • Slinks: Smaller, faster, and more agile than the normal zombies, Slinks appear to be somewhat rubbery in appearance. They are able to contort their bodies in a boneless fashion, making it possible for them to crawl through spaces a normal human could not. They tend to travel in packs of ten or more and while not as tough as a regular zombie, they are clever and use tactics similar to packs of wolves or dogs.
  • Amalgamations: This is a broad classification, including any zombie with non-human parts. Some have claws for hands, others have extra arms or legs. Many have enlarged canines.
  • The Enraged: The skin of an Enraged appears to have huge veins and arteries bulging just under the surface. These throb and pulsate as an Enraged shrieks and gibbers and throws itself after its prey. When an Enraged engages in battle it goes into overdrive. It acts faster and stronger than is humanly possible, often getting in six or more attacks to a human's one and striking with the force of a Brute. They can only keep this up for short periods, however. After a few minutes of active fighting, an Enraged will explode in a shower of blood, guts, skin, and muscle. Anyone around had better be sure they don't get any of that blood in their noses, mouths, or open wounds.
  • Animals: Any number of animal species have been infected with the zombie virus, from cats to dogs to horses and more.
  • Snufflers: These look like tall children who are crouched low and covered in metallic plates. They crawl about, sniffing the ground and air with their snouts, looking for uninfected humans to bite. They move awkwardly but can be surprisingly speedy once they catch the scent of prey.


While the Ch'thra can exert mental control with their sorcerously-induced psychic powers, that only holds while they are within a short range of the target. To keep their agents faithful, the Ch'thra developed a worm which they implant near the spine of a Thrall. This worm acts as a conduit for the will of the Ch'thra. Whenever the worm is within psychic range of its Ch'thra master, it can be set with a program for controlling the Thrall. For instance, the Thralls sent out to gather the first victims were given orders to obtain prostitutes without being detected. A Thrall will carry out these orders to the best of their ability. Once the program has been carried out, the Thrall returns for new instructions.

A Thrall's only purpose in life is to please its master. They will happily throw away their own lives to keep a single Ch'thra safe.

Thralls can be released from their service if the worm is surgically removed. It entwines with the nervous system, so simply ripping one out will either kill or paralyze the victim. All of the Thrall's memories are intact once this happens, making them good sources of information about the Ch'thra tunnels. This also means that many either attempt suicide or become overly zealous rebels once the worm is removed.

The Rift

The Ch'thra do not realize this, but it was an experiment gone wrong which opened the dimensional rift to Earth. The Teth scientist who caused the tear in reality was vaporized in the resulting explosion, along with all of his notes and half a mile of tunnels. The general consensus is that the rift is a rare, yet natural, phenomenon. Rather than concern themselves with creating more, they are content to invade this new world.

The rift goes both ways and appears as a glowing oval of wavy amber. One can almost see through the portal to the other side but not much detail can be made out.

It has been stable for the past ten years and will slowly fade into nothingness over the course of the coming decade. The last couple of years will be unstable; most who try to cross during that time will not make it through alive.

Campaign / Plot Hooks


Where are the PCs when the apocalypse happens? How do they survive when thousands of the sick and dying turn into ravenous undead? How do they deal with the loss of loved ones? How do they survive and where do they turn for safety?


There are many opportunities for good old-fashioned zombie encounters. The dead far outnumber the dwindling pockets of surviving humanity. Most of the survivors have fled into the wilds. A few have set up armed compounds, but many can do no more than hide as far from the masses of hungry zombies as they can.

Encounters can range from attacks by zombies to raids on the cities for supplies to facing the dreaded Ch'thra. Be sure to have them face infected friends and compatriots.

The Slaughterhouse

The Ch'thra have taken a liking to consuming human young. Each city has at least one slaughterhouse dedicated to serving up this ghastly feast. This would be a natural target for heroic PCs to strike at. It will also be heavily guarded. The PCs won't be the first to attempt this.

Curing/Stopping the Plague

If any PCs or NPCs have a scientific background they must feel frustrated at the lack of success in finding a cure. Those wishing to do more than watch humanity slowly ground into dust might wish to find a cure. Or at least a way to change the disease so that the dead stay down.

A raid on a Ch'thra lab would be very risky but potentially rewarding. There is much to overcome in such a plan:

  • Infiltrating Ch'thra tunnels
  • Finding a lab
  • Knowing what to look for
  • Deciphering Ch'thra research material
  • Understanding the sorcerous powers that are a part of the infection.

Despite the dangers, a successful attempt could give the survivors a fighting chance. And while the scholars and scientists figure things out, the PCs could be sent on raids to obtain materials necessary to developing a cure and/or weapons against the Ch'thra and their thralls.

Note: Without the effects of sorcery, the disease does no more than kill its host. Simply put, without the magic component of the disease, the dead stay dead.

Taking back a city

Once they have the tools to fight back, the PCs can step up their game and attempt to take back an entire city. They must face hordes of undead, the living thralls under the control of the Ch'thra, and the Ch'thra themselves. They must also seal off the tunnels, otherwise more Ch'thra and their minions will appear, ready for vengeance. (If the PCs don't realize the danger the tunnels pose, let them find out when a raiding party appears.)

Once they have taken a city, they must figure out how to hold it.

Learning about the enemy

As soon as the PCs have unfettered access to Ch'thra resources they will be able to learn much more about their enemy. There would be many useful tools and weapons of Ch'thra design. This would be a good time for the PCs to learn about the origins of the Ch'thra.

This will not be a time of rest, however, as the Ch'thra will be angry. Assaults will become stronger and more frequent as the Ch'thra seek to put down the threat to their hegemony.

Closing the portal

The first critical step in fully defeating the Ch'thra is to close the interdimensional rift. Once that is accomplished it is a matter of arming the surviving humans and forming armies to wipe the pestilence from the world.

Alternatively, an aspiring group of PCs may wish to take the battle to the Ch'thra homeworld and seek a genocide of their own. Once there, who knows what they will find.

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