Wednesday, November 14, 2018

Cosmic Monster: the Xantherium

The floor was spotless a minute ago, but now a yellow spatter blooms in the stone.  They look like yellow carnations, trampled in the mud.

They do not move--each stain is stationary--but the whole pattern moves, like paint spots dripping from an invisible brush, slowly spreading away from the closed door they seem to have crept under.

They pause for a second, after entering the room, thickening as they darken.  And then then the stains head straight for the two thieves.  They appear like footprints.

From all around them, they can hear the stone groaning in its sickness.

More yellow spots gather, like clouds on the horizon.  They creep up the walls and dapple themselves across the lintel.  The stains are reaching, like the arm of a leper.

Finally, one of the thieves can bear it no longer.  He throws his pack on the ground and sprints across the stain.  He will kick open the door and sprint out, where the sunlight will warm his pale face.

His first three steps cross the yellow stain without incident, but on the fourth, his foot passes through the floor as if it wasn't there.  There is the sound of snapping bone and then the thief is prone.  His leg missing beneath the knee.

There is a moment of cross-section, where the entire meat of the calf is visible, before it is obscured by the profusion of blood.

A second snap, and then his arm is vanished.  Another snap, and another.

Soon there is nothing left of the man except crimson pools.  There is a small sound, like many cats drinking milk at once, and then the blood is gone as well.

The stain has fattened itself, and now the spots are thicker, darker, and more complex.  There is no longer any clear stone between the individual stains, which cover the floor like the roiling of slow smoke.

The second thief watches the murky roses of the stain creep closer.  There is some larger pattern to it.  Here he can see where a certain thickening hints at a low-slung jaw.  On the far wall, there are implications of an enormous eye.

The thief backs into the final corner, an island of grey that is slowly sinking into a yellow sea.  Unless he thinks of something quickly, he will die.

Xantherium (Stain Form)

A xantherium is more like an infection that materials can catch.  Just like rhinovirus colonizes the wet epithelial lining of our throat, so does a xantherium move along the interface of two different materials of vastly different densities (most commonly air and stone).  This is an oversimplification, but it's a start.

It's large.  Maybe 500 square feet (~50 square meters), if it was all gathered in one place.  But it isn't all gathered in one place.  it's scattered around a denser core, like a flock of birds.

You can deal trivial damage to it by damaging the material that it moves through (e.g. chipping away at the stone floor) but it is likely to encircle you before you can deal more than a point of damage to it.

It moves at the pace of a tortoise.  It is attracted to the smell of meat, and a trail of blood can be used to lure it.

Attacks -- It gets 3 bites per turn, no two of which can be made within 5' of each other.  Each attack bites off about a foot of material and swallows it, dealing 3d6 damage.  Imagine a crocodile sticking its snout out of the floor and taking a very fast, very sharp bite.

Weakness -- It has a weakness.  You can pick your own, but I like sound.  Vibrations in the stone.  These drive it back, but they do not damage it.  Any sound lound enough to drive the Xantherium back is also loud enough to incur a roll on the wandering monster table.

Sound doesn't cause it pain.  It's closer to disgust, or religious revulsion.  (Simpler creatures are motivated by things such as pain and pleasure, but the Xantherium is a philosopher, and its prime motivators are philsophical in essence.  However, the mind of a Xantherium is so alien to us that this information is almost meaningless to a prospective interviewer.)

If it is ever cornered by the disgusting chimes, it will manifest itself (nearly) fully in our own dimension.  See below.

Xantherium (Beast Form)

Eight arms sprouting from a shared nexus, shaggy and bilious yellow.  Each terminates in a trio of spade-like claws, which it normally uses to pull itself sideways through space.  (It is a mole, deep down.  If you have a mole in your party it may be able to communicate.  No other creature has a chance.)

Four arms point up, and four staggered arms point down, but they are all the same arm.  (This is literal--any injury to one arm is mirrored on the others.)  It is about 10' tall.

You will only see this form if it is desperate.  Expect it to fight as a desperate animal would.

HDAC none  Claw 2d6
Move dog  Int 6

The Staff of Quiet Bells

A metal quarterstaff, hollow and with an octagonal footprint.  When held against the floor and rung, it creates a muffled chiming that drives the Xantherium away without provoking any wandering monster checks.

If held in the middle and rung overhead, it makes such an ungodly clangor that you can basically pick how many wandering monster checks you want to invoke.  It can be heard up to 3 miles overland, on a dry day.


Honestly, you could leave out the Beast Form and it would probably work better as a Lovecraftian horror.  (If you can kill it with a sword, it's not very Lovecraftian.)

I only included the beast form because that was how I originally conceived of it, and now it persists as a vestige.  I also like being able to make everything in the dungeon theoretically killable, because I'm a completionist at heart.

Is the weakness to sound a good idea?  Maybe.  It's better than fighting the stain with a sponge and soapy water.

You could do light.  Daylight is a little too scarce for a dungeon, though, and the party's only option would be to flee.  Torchlight has the opposite problem, and is a little too easy to provide.  (Sound at least, incurs the cost of a random encounter roll.)

If you were going for something truly Lovecraftian, the worst you could do is something like an emotion.  I mean, it might be fun to have the PCs make out and confess their feelings to each other in order to drive back the stain, but a cornerstone of Lovecraftian horror is that there is absolutely nothing of any value in a human's mind, body, or soul.

Water might be a good one.  (Holy water, perhaps.)  But then you run the risk of the party buying gallons of water in order to trivialize the Xantherium.  (This may be acceptable or possibly desirable, depending on the dungeon.)

This absolutely isn't something that you can just drop into a game.  It requires careful consideration of two factors.

1. What can drive the Xantherium back?

2. How will the players learn of this weakness?


  1. sound works interestingly as a weakness, because if its use does cause a wandering monster to appear, then _that_ encounter has some built-in terrain that both parties can take advantage of - the xantherium.

  2. This plus the last post will definitely make it into that Esoteric Enterprises stuff I want to do.

  3. I'm digging the concept. As for learning the weakness, there are plenty of options.

    1. Research. If you go to a library and spend some campaign downtime reading books, or pay a sage to do it for you, you'll find hints that loud noises or music seem to work to upset the stain.

    2. Word of mouth. Sentient monsters in the dungeon could be convinced to tell you about greater threats than themselves in return for mercy or barter.

    3. Learning by example. Sentient monsters in the dungeon carry chimes to protect themselves against the stain, or certain areas are guarded by a perpetual-noise machine of some kind - a xylophone placed under a waterfall's spray, for example.

    4. Other dungeon hints. Wall art, a previous explorer's notes, a noise-maker with an inscription, etc.

    5. Knowledge skills. If you have them and a player rolls high enough, maybe they remember a tale about how a bard managed to ward off an unstoppable beast through song and drum, averting a TPK for their own expedition in years past.

    6. Magic. One of the under-used assets brought by spellcasters in general, and clerics in particular, is divination magic. This is exactly the kind of situation it's in the rulebook for.

  4. I was thinking rooms with huge, inexplicable bells in them. Highly immobile bells.

  5. Piggybacking on the idea of travelling on the edges of disparate materials:

    If they travel on the edges of earth and air, pouring water, say to a depth of a few inches, disrupts that edge, and acts as a wall. But additionally, they could travel along the edge of any two "opposite" elements. Steam, being the edge of fire and water would make for a temporary and potentially dangerous bridge.

  6. Sound works great. It takes some figuring out, but you can give some clues as per confanity above, and it's a bit reminiscent of how Spider-Man used to deal with Venom, back in the day.

    Agreed that the beast form is unnecessary. If you don't want the PCs pushing it around once they discover its weakness, have it gradually develop a resistance to a particular type of sound. It's up to you how granular you want "particular type" to be. Like, if you drove it off with string music last time, will drums work next time? Or have you eliminated all sorts of music and now only shouting works?

    Alternately, have it vulnerable to only a particular sort of sound: flutes, say, like a classic shoggoth. And, hey, have the PCs find a flute in the dungeon! Mention in passing that it's really old and seems very fragile, like it's made of glass. Then, every time that PC is in combat or takes some violent action, give the flute a chance of breaking.

    "Moves at a tortoise's pace" is fine, because -- unless it herds the PCs into a dead end -- it's a timer as much as a monster. (You have four rounds left to finish up in this room before it cuts off your escape...) Which is fine because if I'm reading this right the stain form simply can't be attacked. A thing that can't be attacked, however hopelessly, isn't exactly a monster any more. But it can still be creepy AF.

    One minor issue: PCs who can levitate or, worse yet, fly are simply immune to this monster. I have the impression that these abilities are rare in your games, which is fine, but if you ever want to port this guy into Pathfinder or 5e that's a hole in the concept. (Pathfinder positive here, but things like "by midlevels every party has lots of flight spells" and "pretty much everyone has darkvision" do make me sigh.)

    Doug M.

    1. The idea that "it develops antibodies against certain types of sounds" is an interesting one. I like it.

      I agree that the beast form is a little off-theme, but it *is* very surprising. And there's a little bit of precedent: old cosmic horror stories were full of weird ideas like transmuting starlight into life forms, or imprisoning people in the ancient past. This is, maybe, a little similar.

      Anyway, beast form would be nicely surprising.

      To use in mid-level PF, just let it cast *disintegration* on an adjacent point, or any point between two patches of the stain, and then just have it grow to cover opposing walls.

  7. "a cornerstone of Lovecraftian horror is that there is absolutely nothing of any value in a human's mind, body, or soul."

    oh no no. There can be value! The Yithians want to ride you around like a borrowed car. The Mi-Go want your brain to experiment on. Yog-Sothoth will have sex with your daughter because it wants to create a half-breed child to end the world. The Hounds of Tindalos find your attention annoying and will dismember you for it. And there are a bajillion Mythos creatures who will flat up eat you.

    What unites the Mythos is that not that you don't have any value, but (1) you have at most *minimal* value -- as a toy, tool, experimental subject, breeding animal, or snack; and (2) the value system is alien and almost certainly hostile.

    Oh and tbf yeah sometimes you have no value. You're just vermin (Call of Cthulhu) or collateral damage (Colour Out of Space).

    Anyway: feeds on emotions is bad, but /affects/ emotions isn't necessarily. The Colour Out of Space is terrifying in large part because of the apathy it infects its victims with. A monster that affects volition, cognition, or self-control *just by its presence* could be pretty creepy. "Being around it fogs your mind and it becomes harder to thing. Every round you're in the same room with it, lose a point of Int, no save. You gain back a point of Int per minute once you're out of the effect... but if you go below Int 3, you're permanently an animal." Or some such.

    Anyway, obviously I'm liking this. Please continue.

    Doug M.

    1. Man, Yog-Sothoth could destroy the solar system as easily as it could blink.

      This is all headcanon, by the way. This is Yog-Sothoth as I would write him.

      I don't think Yoggy impregnated Lavinia Whately in order to destroy the world. I think Old Man Whately exploited Yog-Sothoth in order to grab dominion for him and his son, perhaps analogous to situation where ants steal insecticide out of the shed in order to use it against their enemies.

    2. I guess I'm thinking about Cosmic Horror more in relation to the cosmology, and how it relates to the human soul.

      Strange monsters that want to eat you, sure, fine, but the real horror is what it implies about the rest of the universe.

    3. I like the insecticide analogy.

      Doug M.

  8. I think vulnerability to light would be ok, if it was proportionate to brightness. A lantern or a torch might only be enough to create a tiny safe ring or spot, so they would have to work as a team to herd it and stop it leaking between the pools of light, or perhaps they could block a doorway, or create a safe path for one person at a time.

  9. It's fun, but a little too physical for my taste. I'd like if you could tie it to Chambers "The Yellow Sign" and Gilman's "The Yellow Wallpaper," or at least as another form where it eats at souls and sanity.

    1. Nibbling at souls and sanity is great, but it's always a bit tough to make satisfactory mechanics for that anyway. Character minds are tricky to meddle with.

      Player minds, on the other hand. . .

  10. Item idea that works pretty well with this.
    Clangor Jelly: Nearly translucent gel that creates a loud clattering sound when compressed, eventually hardening into a flaky crystal. It could be encountered covering certain portions of the floor, first as an obstacle that attracts wandering monsters, and later as a protection against the xantherium.

  11. Striking the floor with a outclassed might not damage the creature, but the noise of pick on stone might dive it back for a moment. Which could well lead players to come to the wrong conclusion about why it's fleeing. This is, of course, the point.

  12. Coming back to this on a reread.

    The density interface thing: stone is ~1000X more dense than air. But it's only ~3X more dense than water. So, if you poured water or some other liquid onto the stone floor, that might block its movement.

    Note that this could lead to a party pouring oil onto the floor to light it on fire, and drawing a badly incorrect conclusion.

    Doug M.