She was a little naive, but very sweet and thoughtful and trying her best.
Rather than running on an underlying set of rigid physical laws like most worlds, her world was primarily conceptual. Everything in Mareth has an essence, which forms the structure that allows it to maintain consistent properties. Different types of things have different types of essences, as follows:
- Everything with any sort of physical form has a material essence, which is the substrate holding its consistent physical properties. The material essence of a rock reminds the rock that it is hard and dense and heavy and has a certain colour and so on; the material essence of water reminds the water that it is wet and transparent and fluid.
- All living things have a lifeforce, which is the substrate holding their consistent biological properties; it organizes the physical properties of their material essence into the coherent structure of a living being. The lifeforce of a dog reminds the dog that it has four legs and two ears and a nose and its fur is like so and its organs all go in their places and function in their ways.
- All sapient beings have a soul, which is the substrate holding their consistent mental properties. A person's soul is like the skin of their mind, holding in place to ensure that none of the bits fall out and maintaining a barrier between it and the outside world. It's possible to remove a person's soul, and you won't even notice any immediate effects from doing so, but their personality will start to destabilize and they will tend to become inconsistent, impulsive, may develop problems with long-term memory, and other such issues.
One notable quirk of this essence-based system is that it's nearly impossible to kill someone by accident. Soul governs lifeforce, which governs material essence in turn, and most people's souls are pretty firm on the fact that they are and should remain alive. In order for someone to die, one of two things must happen: either their lifeforce loses the power to maintain itself, such as through old age, illness, starvation, or truly catastrophic injury; or another person deliberately injures them very badly, and their own will to live is overcome by the other person's will to harm. If two people are fighting and neither wants to kill the other, it's very, very rare for one of them to die. (So one of the other drawbacks of losing your soul is that, although you will still have a mind and will of your own, it will be much, much weaker than nearly anyone else's, and you will be correspondingly easier to kill.)
The first people in Mareth were humans. Eventually, humans invented alchemy, which is the science of extracting and combining essences from things in order to produce magical effects. One of the easiest alchemical inventions is the transformation item: for example, if you create an alchemical extract that applies the colour pink to things, and apply it to your hair, your hair will become pink. If you create an alchemical extract that applies dog ears to creatures, and apply it to yourself, your ears will transform into those of a dog. Naturally, people started experimenting with these, and this led to an explosion of different varieties of person with different sets of features.
Outside of special cases such as dragons, most nonhumans can be categorized as one or another type of animal-morph: bunny-morphs, dog-morphs, cat-morphs, fox-morphs, horse-morphs, and so on. The standard animal-morph body plan is still bipedal like a human's, though they may add wings or a tail; cases such as what we would call centaurs and naga and driders are called caudal morphs (caudal horse-morph, caudal snake-morph, caudal spider-morph), because they substantially alter the 'tail end' of the body.
Once you have an established body plan that you like and want to make easily available, you can use advanced alchemy to create a renewable source of transformation items targeted to that body plan, for example by engineering a species of plant that grows transformation-inflicting fruit (whisker-fruit, canine peppers, fox berries), or by including the ability to produce transformation items in the body plan itself (pink gossamer, pure honey).
By default, these generic transformation items will tend to apply a random small subset of target traits to the subject when consumed, and are often only partially successful at that (e.g. giving someone scaly legs rather than a proper caudal snake-morph tail), but you can also use simple alchemy to focus such an item toward a single specific desired trait. Generic transformation items have a nearly indefinite shelf life, but specialized ones have to be consumed fairly soon after they are made.
Also, even with focused transformation items, it's nearly impossible to accomplish an entire transformation from e.g. human to caudal shark-morph all at once. An active lifeforce has a natural resistance to sudden drastic changes in its body plan, and the mind's concept of its body's form lends the weight of a person's soul to that resistance, so under most circumstances transformations need to be gradual and piecemeal; you can overcome some of that resistance by wanting the transformation, but not all of it. The soul also imposes some limitations on the extent of possible changes: most people will find themselves incapable of transforming into the shape of an animal with no remaining human features, or a seven-headed dragon, or a thirty-foot-tall giant, because even with gradual piecemeal transitions there's a point where the soul puts its foot down and says 'no, absolutely not, I can't conceive of myself this way, it's not happening'.
Besides alchemy, the other main form of basic magic in Mareth - usually referred to simply as 'magic', or sometimes called by more specific terms denoting particular schools or traditions - is the art of focusing your will in order to affect the world around you. This can be as simple as lighting a fire or as complex as enchanting a door to remain hidden to anyone who doesn't know the password.
As civilization grew and spread and diversified, different groups of people began to have different preferences about their environment to such a degree that Marae couldn't accomodate them all within a single world. So she began to divide the initial world into multiple discontinuous locations with different properties. Mareth stayed at the center, and portals opened up to a wide variety of new and different places. One world was made for people who liked to fly, and it had no bottom, only a scattering of floating islands in an endless expanse of air. One world was made for people who preferred as little magic as possible in their lives, and it gave material essence much more weight and stability in the scheme of things, so that only the simplest and most direct kinds of alchemy still worked, and nearly all the behaviour of physical things was dictated by the interactions of their physical properties.
And then some foolish and overly ambitious people invented demons.
Their intentions were more or less good. They wanted to be able to do more powerful and interesting magic; they wanted to be able to live forever, unbound by the slow decay of age; they wanted to push the limits of alchemy and magic, achieve greater sexual and morphological freedom, and make fascinating and unprecedented discoveries about the nature of reality.
Technically they accomplished all those things.
The trouble started when they began experimenting with the removal of the soul.
A soul, by its nature, is a tremendously powerful thing. Just as lifeforce must be stronger than material essence in order for a creature's lifeforce to impose the form of its living body on its material components, soul must be stronger than lifeforce in order for a person's soul to impose the form of their personality on their mind and impose the will of that mind on the world around them through magic. And up until this point, no one had actually figured out what a soul did exactly, but they were pretty sure that it wasn't strictly necessary to have a soul in order to continue being a conscious entity with thoughts and feelings and memories. So what, actually, did souls do? And could they be repurposed as power sources?
They were, to their credit, very careful with their experiments. They found ways to suppress certain functions of the soul, vastly increasing the potency of their transformation items by circumventing the subject's natural resistance to drastic changes of form. Encouraged by this unqualified success, they tried suppressing all the soul functions they could access for a few minutes at a time, piecemeal and then all at once, and found that there were no discernible effects on personality or memory. They separated a person from their soul completely, ran some tests on it, and put it back: it worked fine, no harm done. Their volunteers could survive an hour, a day, a week without their souls, and apart from a few minor issues easily attributed to the stress and excitement of the project, and the expected increase in susceptibility to injury and transformation, they were fine.
So they moved on to the final phase of testing: the head of the project removed her own soul, used its power to enhance her chosen transformation item, and drank it.
And she became the first succubus, and soon afterward the Queen of Demons.
In addition to their experiments with soul removal, they had also been looking into using lust as a source of magical power; it's an obvious idea to explore, because magic is an exercise of the will and lust represents a very powerful and primal focusing of the will. They weren't even the first people to try it. It made perfect sense, from their perspective, to include amplifiers for lust-based magical power in their demonic transformations: after all, they were trading in their souls for immortality, and the power of the soul is a substantial part of what makes magic work at all, so they needed some way to compensate for that. And, as many people do, they liked sex, so it seemed like it would make a comfortable and pleasant power source.
But what happens when you create a comprehensive transformation potion imbued with the most potent possible forms of power amplification, focused specifically on lust and lust-based magic, designed with the intent of reaching past the boundaries of mortal limitation to grasp eternal life and unimaginable power, and then you give it to someone whose mind and personality are now stripped of all their defenses against external influence - and who for that matter was pretty ambitious and sexually adventurous to start with?
Her former personality was pretty quickly reduced to a mere sprinkle of inconsequential details and fading memories atop a vast, violent, all-consuming drive for sex and power. Those of her colleagues who refused to join her budding demonic empire, she either transformed coercively or killed outright. (It's technically not possible to lose your soul without an act of will, but that doesn't preclude being tortured until you agree to give it up.) They raided nearby settlements to kidnap and enslave their citizens, using them for sexual entertainment or magical fuel or both. The power they gained, they used for conquest, and their conquests brought new sources of power.
Demonic corruption is a magical force created by that initial transformation. It is present in the bodies of demons, in their flesh and blood and especially in their sexual fluids, and to a lesser extent in the bodies of beings that are very corrupt but have not yet completed their demonic transformation. It empowers and amplifies lust and lust-based magic, and its influence pushes people toward a more demonic state of mind, emphasizing sex and power to the exclusion of other concerns, encouraging rape and violence and the subjugation of others.
But no matter how soaked in corruption a person becomes, it's still possible for them to reassert their identity and find a way to purify themselves... until they give up their soul, at which point they're just another demon, with no will of their own left to oppose their demonic urges.
One of the first things Marae did when she noticed the problem was close all the portals, making it very difficult to get into Mareth itself and nearly impossible to get out. If the demons had started out in one of the demiplanes, maybe that would have been the end of it, and they would have stayed bottled up in their own little world, raping each other forever. But they started out in Mareth proper, and she didn't have the power to banish them into a plane of their own.
This was very effective at keeping all the demonic corruption contained in Mareth proper without any of it leaking out into the other worlds, but now Marae was trapped in her own realm with slowly rising levels of ambient corruption and no good way to stop it. She could purify individual people and places, but she couldn't fight the demons herself; Marae has the strongest soul in the world by a wide, wide margin, and one of her core personality traits is not wanting to hurt people, so she literally can't harm anyone directly or change their nature against their will, even if their nature is "bloodthirsty all-devouring avatar of rape and conquest" and even if the person they once were would probably have preferred not to turn into that.
She did her best to purify and empower the people trying to fight the demons, but the corruption eating away at the heart of her world-self hurt, and after a while of watching people fight and die and be corrupted into joining the other side, she gave up and retreated to a magically hidden island in the middle of her favourite lake. The demons, able to discern her general location but not able to track her down and attack her personally, settled for building a demonic factory on the lakeshore where they could pump hundreds of gallons of corrupt sexual fluids into the water on a daily basis. The factory's ultimate goal is to corrupt Marae herself, and thereby reopen the portals and gain access to all the other worlds.
Speaking of the other worlds: the portals are very well-sealed, particularly against demonic corruption, but it's still possible to pass messages through them and occasionally even send a person, especially if they're traveling into Mareth rather than out of it. The demons make a habit of examining every portal they find and figuring out how to communicate through it, then trying various combinations of bribes and threats until they get the people on the other side to agree to periodically send someone through the portal. They like the variety, they find these outworlders are often easier prey than the better-informed locals, and they hope to eventually figure out how to break open the portals and conquer the worlds on the other side.
Some outworld settlements are more receptive to these arguments than others. In canon, the protagonist is an ordinary citizen from a village called Ingnam, which lies to its yearly sacrifices and tells them that they are "champions", sent through the portal to defend the village and the world beyond against the demonic hordes that might otherwise come through to conquer them. Ingnam appears to be situated in a very low-magic sort of world, with no discernible animalfolk and barely any alchemy, which is why I surmised that the nature of reality must differ between different planes of existence.
I had to invent a lot of the underlying principles in this post in order to explain the observed phenomena in the game, and in the course of doing that I ended up having to change some details, but overall I think I did a pretty good job of turning CoC into a world that makes enough sense for me to glowfic.
