The way I usually explain how alchemy works is the existence of two magical substances. Essence is the fundamental basis of alchemy, and it arises from the dreams and desires of a conscious brain. Why this is so is oft‍-​considered one of the great mysteries of the world. But essence is innately unstable and reactive; whenever it comes into contact with physical matter, combustion‍-​subsumption results and together they create limina.

This is the other, more outwardly obvious magical substance. Limina has mass and more stability than esseence. It is able to coexist in the physical world. But it can also shield essence from interaction with matter, allowing it to persist.

Imagine pouring dirt into a puddle. At first it becomes wet and turns into mud, but after some of the dirt is sacrificed to form that first layer, the dirt piling atop it remains dry. Essence reacts to produce enough limina to protect itself.

Essence has a lot in common with electricity; it flows and creates a field for forces to act at a distance. Limina‍ ‍‍—‍ despite its mass‍ ‍‍—‍ is exceptionally easy to reshape, especially by manipulation of the essence field. The ancients called it “divine clay.”

But I did not describe limina as stable, only more stable. If starved of the flow of essence, limina will undergoes a kind of collapse back into almost‍-​ordinary matter. But since limina was so easy to reshape, you can see a utility in this process: first transform matter into limina, then mold it into a new form, then siphon off the essence, and behold how easily you reshape the world.

Those with honed phyisical instincts may expect a conservation law. If essence + matter = limina, and this product presists as long as there is excess essence, then shouldn’t the collapse of limina back into matter also return the essence that created it? Otherwise, where does it go?

The mathematics aren’t so kind. Essence is changed through its affair with matter; it cannot return with the same purity it once had. Instead, it becomes a sort of anti‍-​essence. Where essence could not bear the presence of matter without reacting with it, this byproduct is perfectly able to persist, clinging to objects like static fuzz. An object imbued this way is considered transmuted.

With some abuse of language, we might refer to this “anti‍-​essence” as transmutation. And the distinguishing feature is that transmutation violently combusts with essence, preventing the formation of more limina, or that mysterious genesis of essence ex nihiho.

Because essence originates in the brain, and because the flow of essence controls the form of limina, alchemists consider these substances to form the soul, the chief organ for practicing metaphysical work.

In a layperson, limina seeps throughout the body, circulating through the blood, but without disciplined control of their essence flow, at their extremities limina often collapses into transmutation, resulting a messy patchwork of essence‍-​laden limina and transmutation.

Matter cannot be shorn of its transmutated nature except at a cost of energy‍ ‍‍—‍ even still, expelling the “anti‍-​essence” often creates explosive forces that threaten the structure integrity of the transmuted object. In bodies, this means tissue damage. This is the difficulty of the alchemists’ first task: compleating the soul.

Simply burning away transmuted impurities would cause lacerations and fissures throughout the bodies: it would prove swiftly fatal. Thus the transmutation must be cleared away slowly, carefully. Slowly enough that even as you remove one impurity, more transmutation in being ingested or created by the body’s metabolism. It is no mystery why this process can take years.

But there’s a further wrinkle. I mislead you, which I told you that transmuted impurities arise through the laity’s lack of control. No, the fundamental contradiction of alchemy is that a single brain cannot generate enough essence to compleat a soul. It is akin to flying by tugging on one’s own bootstraps.

The body bears the stain of transmutation as an inevitability, the high banks of river will on occasion know the touch of its waters but the flow is never sufficient to flood the it to the brim every day of every season.

Even the wisest alchemists, acquainted with essence’s origin in the dreams of mortals, cannot generate enough of it, not at a rate appreciably faster than the a lay fool. In this all mortals are largely equal.

No, the only way alchemists are able to sustain themselves is by supping on the essence generated by vigners and offered in the fruit of their vines.

Hearing all of this, you would naturally come to the conclusion that essence is a very scarce thing, as if each mind is mining some precious gem from the inscrutable depth of the world.

This is the belief that the Aether Brain Hypothesis challenges.

It suggests that essence is in fact just abundant as the air surounding us. Or perhaps not essence itself. Rigorously formulated, this conjecture introduces a third class of phenomena: the titular aether. Aether is furtive and unreactive, able to suffuse every inch of the world without revealing its presence.

It is attracted to matter, trailing in its wake, and dutiful reënacts its every motion. For this, theorists have been moved to imagine an “astral plane”, identical to the material world, but composed of this aether pantomime.

This equivalance between material and aether is the Grand Symmetry. But grand as it is, it is only notable because it not perfect. In animate bodies, the aether counterpart diverges subtly from its source. Romantically, we might imagine the astral imitation is unable to cope with the vagaries of free will.

A more mechanical explanation is substances present in living bodies are what break the symmetry. Small particles that interact with matter and aether both, yet discriminate and perturb the symmetry.

Imagine inviting men and women to a dance, each paired with the opposite gender. Now suppose someone tampers with the records, skewing the balance of genders and making a confusion of the intended organization. Instead of a perfect one‍-​to‍-​one pairing, strange new dances emerge, multiple men competing for a woman (many to one) or a man with several admiring women (one to many) or girls dancing among themselves (zero to one).

Aether, remember, was supposed to imitate the behavior of matter. But this imitation isn’t idle‍ ‍‍—‍ aether does have mass. When it is dragged in the wake of matter, matter likewise falls back to join it. Because of the grand symmetry, this two‍-​way interaction can be ignored: aether’s influence simply redundantly reduplicates the motions of matter. When they diverge? Matter will be dragged astral.

Consider a one‍-​to‍-​many interaction. Here, several subdivisions of the aether field have mappped onto the same material element, and as a result, the stablizing influence of aether is disportionate. In order for the matter to move, it must tug on not only the usual aether hanger‍-​on, but several others who cling to it.

Many‍-​to‍-​one are more interesting to contemplate, owing to the fact that two objects cannot overlap in space, meaning that this aether acts to synchronize several similar objects to a shared state.

Zero‍-​to‍-​one are the strangest by far. It is as if the astral plane was twisted, subducted into itself, causing aether to imitate aether as if it were matter. But this is self‍-​referential, and consequential any behavior becomes self‍-​justifyingly possible.

One theory posits that “essence,” “limina” and “transmutation” are no more than phases of aether, geometric arrangements of this deviations in the Grand Symmetry. But perhaps a rigorous reduction of alchemy to aether is beyond the scope of this discussion.

Step back, and consider the true implication of this astral plane. It’s nothing less than a doubling of space, with profound implication for processes which find themselves limited by space. Could Book could be bound to take up half as much space if every page had not two sides but four?

Remember that we supposed living things bore substances that broke the Grand Symmetry. The Aether Brain Hypothesis proposes that the brain deliberately alters its cognition across the material/aether split to exploit the duplication. This aether divergence is used to not just to accelerate thought, but to rapidly signal and synchronize across cortices. It is in fact essential to the emergence of the unified experience of consciousness.

Biologically, all brains would perform this operation to greater or lesser extent, but it is of course the most acutely developed in the most intelligent species.

If the sea of aether is everywhere around us, but only in brain is there turbulence enough to subduct and create those zero‍-​to‍-​one “bubbles” that are unbound to matter… have we not arrived at an explanation of just what essence is, and why brains alone generate them?

But what is unique about cognition? What stops us from isolated the molecules that give rise to this phenomena and generating abiotic essence, perhaps stirring them in a warm pot?

Key to what’s happening isn’t that the Grand Symmetry is breaking, but that it’s breaking in a structured, useful way. Why not create food by putting amino acids into a warm pot and stirring it? Only metabolism creates the proteins that life requires, and only brains produce the emyra that is the true power of essence.

It is possibible for inanimate objects to produce noises, and animals can produce complex calls indeed, but only sapient animals produce language. And it is the complexity of emyra, the self‍-​modifying recursive flows of essence, that allow for alchemy as such.

But what happens if you insist on trying to replicate the production of emyra through nonsapient means?

The result is chimeric.

Occasionally, especially through illness and defect, an animal may secrete a surplus of the molecules responsible for symmetry‍-​breaking. Much like a virus or cancer replicating without bound, there are essential metabolisms that self‍-​catalyze.

Sapient brains are slow to generate essence because they use that essence to do useful work, coordinating billions of neurons and exciting delicate pathways. But lower animals do not rely so heavily on aether effects to accelerate their thinking.

If a human folded aether at the same rate as a chimera, their mind would collapse into seizure and agony. Their soul would dissolve into chaos.

And the chimera is not unscathed by this alchemical firestorm. Yet it has so much less to lose. The result is that it is able to generate a tumor‍-​soul, quickly gaining mass to rival the most distinguished alchemists, but with little more than brute strength to show for it, because rather than the crystalline, multifaceted brilliance of a third compleation master‍-​soul, the chimera has a bloated mass of mad‍-​dash cancer‍-​growth.

But chimeras reveal a new complexity. I have compared the vast volume of aether to the sea, or to the atmosphere. And yes, it is an abundance, particularly compared to the meager volumes that determined alchemists draw forth. But it would be a mistake to misunderstand the quantity of aether as infinite.

Chimeras highlight this folly. This is the origin of the “miasma” that renders these beasts such a fearsome threat. Because they greedily, incessantly suck up aether to fuel their growth, chimeras disrupt the aether that allows mortal brains to function. The result is akin to carbon monoxide exposure.

Thus the chief duty of alchemists: to hunt down chimeras.

This theory has further applications in illumination two major developments in the world’s history.

The first is the origin of arachnophobia. There once was a race of intelligent spiders called the Forspun. They were predators, hated and feared across the Verdant Halo. Despite their intelligence, they were considered just as incompatible with civilization as chimeras. Yet by all accounts, they had mortal souls. What explains this?

It was a curious feature of Forspun biology: their venom. Their fangs delivered a potent neurotoxin which reacted with flesh to break the Grand Symmetry. Prey dosed with Forspun venom experienced the same seizures and brain failure as chimeria miasma induces, and at high enough doses, it will in fact radiate the same “aura” of dysfunction that chimeras exude.

Some nuances of taxonomy are justifiable, but to simplify matters‍ ‍‍—‍ and to echo the warnings of legend‍ ‍‍—‍ the Forspun were able to create chimeras with their venom.

But again, they had complex souls like any other mortal. Surely this amounts to sword held by the blade? Not quite.

Again specific taxonomy is more distinguishing, but to simplify, the Forspun were the first alchemists. Much like how vigners can share essence in the fruit of their vines, the Forspun could imbue essence into their silk‍ ‍‍—‍ their serivane.

(It is no coincidence that transmutation circles resemble webs.)

When hunting, the Forspun would don serivanescent veils woven aether‍-​tight. When subjecting their prey to chimeric agony, the miasmic ination of the air could not penetrate their bubbles of aether bound within their veils.

The Jet Blasphemy was among the great crimes of the last empire; they discovered deposits of a magical mineral that could be burned to produce usable essential in great quantities, freeing those mortals of their dependency on vigners and their laws.

The externalities of jet combustions are best explained as a vignet equivalent of Forspun venom. If chimeras have a disabling effect on mortal minds, then jet pollution is just as brutal on the vines that had granted alchemists their power.

If you know where the Jet Blasphemy had lead, then you are perhaps wondering how chrylurks fit into this picture.

Chrylurks are, at heart, an attempt at creating a wholly new form of life. The mortal metabolism constantly works to generate more emyra. This is despite that fact that alchemists do not even generate most of the emyra they wield, relying instead on a surplus purloined from vigners.

Would it not be more efficient if instead of a meager trickle of emyra, a creature existed for which all resources were honed toward using emyra sourced from others? (In this way, chrylurks parody the mortal dependence on vignet fruits.)

But the new possibilities are deeper than that. One of the dogmas of alchemy is the transmutation of brains is impossible, because its cathexis means that organ is always clad in fresh essence.

Because this is not remotely true of chrylurks, they are capable of transmutating their brains. Much more ought be said about how this impacts their cognition; it deserves its own write‍-​up.

When chrylurks aren’t transmuting their brains, they are capable of quiessence, a state of total invisibility to mutamyric perception. Alchemists are proud of their all‍-​penetrating arcane sensitivity. These soulless husks are thus so unnerving they are considered to exist in the state of blasphemous unlife.

Lastly, a curiosity must be noted. Recall that transmutation violently reacts with essence. So much the atrocity inherent in chrylurk life is a consequence of their need to siphon the essence of mortals. But mortals themselves consume the essence of vigners. Could we not achieve peace of chrylurks adopted a vegetarian diet?

But chrylurks do not depend on essence‍ ‍‍—‍ they specifically depend on essence in the form of nectar or sanguimel. Emyra, the quasi‍-​molecular structures formed by aggregation of essence, are not created equal. Nectar bears a form of emyra tailored for chrylurk metabolism. Ambrosia has its own unique properties. Vigners were bred, generation after generation, do help alchemists compleat their souls.

Souls are made of essence, it’s why self‍-​transmutation is impossible. Chrylurk cognition, though, requires neural transmutation.

Which to say: chrylurks cannot drink ambrosia because it would give them a soul.