Imagine a 2-dimensional world, full of 2-dimensional castle and 2-dimensional people. Now imagine a person standing to the left of that world, so that their body doesn't intersect with it in any way. Now imagine that they have a couple of paper puppets, and that they insert into the 2-dimensional world, making them stand on top of that 2D castle as if they belonged there.
Now you know what a geminoid is.
a 2-dimensional drawing of a 4-dimensional fellow
and the geminoids should be larger relative to the puppeteer
Their shapes are crude, with odd ridges and flat spots, like wax pressed into the shape of a human. They seem like imitations, because they are. They wear thin cloaks to obscure their clumsy shapes.
They are hand-puppets, pieces of a much larger creature that is projected into our world. The puppeteer cannot be seen, cannot be felt, cannot be heard, cannot be smelt. It is sideways to our world, and you cannot reach it any easier than Mario can turn sideways and leave your television.
Beneath their cloaks, they do not wear much. They are always hot to the touch. The puppeteer, floating in the vacuum of the void, struggles to radiate heat. There is no air there. And so the hand-puppets must manage the temperature of the entire beast.
Sometimes the puppeteer relaxes, and turns the puppets slightly sideways. One arm might shrink to a stump; another arm might grow thick and untextured. A normal-seeming eye might relax into a colored spot on featureless skin, like a giant freckle. If you pull back the hood of a sleeping geminoid, this is what you will see.
(I will speak of geminoids in the plural. This deception is for your players.)
Their arms are as bony as their fused ribs. Their legs are thick, calloused things, made to support more weight than you'd expect.
If you watch closely, you will notice that geminoids don't seem to breathe. Their extra-long breaths form condensation in cold places, but their chests don't rise and fall. This is because the lungs are in the puppeteer, not the puppet (although the puppeteer must still breath through his hands).
Inside a geminoids spindly body, you will find almost nothing except muscle, bone, and circulatory system. Some of these will seem illogical or impossible, such as an artery that forms a loop with itself, and connects to no other part. (Their heart and lungs are located inside the puppeteer--you will not find them.)
|what looks like levitation is really just a geminoid raising its hand behind the scenes|
Geminoids can hit you a lot harder than you think. (A hand-puppet curled up into a fist can hit you a lot harder than a man the size of a hand-puppet.)
HD 6 (HP 24) Def chain Slam 1d10 each
Move * Int 10 Mor 4
If you define them according to the format of a game system, geminoids have a lot of abilities. But once you grasp the concept, it's really simple.
Shared Body -- Geminoids share an HP pool: 24 points. They also share their weight, which fluctuates depending on how much of the overall creature remains in the void (which has no gravity). They share a blood supply and a mind. They function as two creatures against AoE damage, but against spells that target creatures, treat them as a single creature.
Flight -- One geminoid can fly anywhere within 20' of the other geminoid, provided the other geminoid remains on the ground. (This is equivalent to the puppeteer using one hand to pull themself higher while reaching with the other hand.)
Exit -- A geminoid can leave our dimension. This looks like the creature being sucked down its own bellybutton, and then shrinking until it is just a small sphere of flesh the size of a basketball. It looks like new types of skin are flowing from the asshole on the back of the basketball and swirling down the bellybutton on the front. Smaller and faster and then it is gone. (This is equivalent to the puppeteer taking his hand-puppet off the stage.)
The puppeteer needs to have both hands in our dimension in order to hold on. Without at least one geminoid to anchor it, it will come untethered, and starve to death in the void.
A geminoid can grab a character and pull them sideways into the void. This requires one turn to grab, and another turn to pull them sideways. The character gets a Cha save to resist, and if they are holding on to something, they also get a Cha save. If they are tied down, the geminoid must break the ropes before it can pull them sideways.
Once a character has been pulled into the void, they gain 5 Trauma and begin to suffocate and overheat. There is no light in the void. The geminoid can attempt to throw them away or pass them to the unborn twins (see below).
Entrance -- A geminoid that is in the void can enter the world the same way it left. It can appear anywhere within 20' of its twin, even on the other side of walls.
The puppeteer may carry items on its extradimensional body, similar to a bag of holding.
Unborn Twin -- Every geminoid has 1d3-2 (min 0) immature buds. The yare the unborn twins gestating in the void, like unfinished hand puppets. If it needs reinforcements, the geminoid can put these unborn twins into the world, effectively doubling the number of geminoids. The unborn twins have the same stats and abilities as their siblings, they just look wet and unfinished (because they are) and have AC as unarmored.
Full Entrance -- The puppeteer has no reason to ever enter our dimension. It has no reason to. Besides, it is too Thick to exist here, much like a puppeteer can never put their whole body atop a paper-thin diorama. (The only reason I can think: it might need to pass its body through our dimension to hide on the other side from a larger predator.)
Still, nothing is preventing the puppeteer from pulling its whole body sideways and materializing in front of a stunned party. This would make it look like an inside-out octopus, with each of its four tentacles connected to an inside-out human. Viewed from the side, its head looks like a three-dimensional version of a CAT scan of the human head, magnified to monstrous proportions.
|These would be inappropriate structures for Super Mario World|
A geminoid's true body is an inappropriate body for our world.
When describing geminoids and the puppetmaster, remember that they are not natives of the Void. (True natives have no interest in an incomplete dimension, and would actually struggle to affect it in a systematic way.)
This is because they were human before they were aliens. They have adapted to the liminal spaces between worlds, like penguins, pelicans, or flying fish.
It is believed that the first proto-geminoids were created by mishaps while investigating extradimensional spaces. (Beware the bag of holding. Never allow the extradimensional space to detach from the burlap and attach to you.)
They are not a true species. They are created by the induction of a fourth-dimensional uterine prolapse during the first trimester.
Their minds are completely human. They are not Outsiders. (But they know strange things. They have met Outsiders.)
When they are born, they seem almost like a regular pair of twins. The puppeteer is still undeveloped at this point, and they seem like two creatures instead of one.
The easiest way to test a newborn is to attempt to separate it from its twin. Newborn geminoids cannot be moved more than a few feet away from their twin.
If you forcibly try to separate a pair of geminoids, you might rupture their sac-like body. Their blood will spill out into the Void, and the two babies will blanch, weaken, and die.
More likely, though, you'll just succeed in pulling the baby sideways. It will volute in your hands, shrinking through a thousand stages of deformity in the second before vanishing.