Biology of magic use and magical exhaustion

Table of Contents

Excerpt from the textbook The Biology of Magic by Irène Norlie.   Out of all living organisms, humans are the only one with a particular biology quirk that gives us unequalled talents in manipulating magic. However, they also give us a higher risk of injury and permanent body damage as a counterpart. The most common of those risks is magical exhaustion, a common condition that will affect every one of us at least once but that can still have grave consequences. Unfortunately, efforts to prevent it are not so successful when the temptation to use magic beyond one's limits is so strong.  

The anatomy of magic

Humans can use magic thanks to a combination of different elements:
  • a reserve where magic particles are stored,
  • magic channels that allow magic to flow through the body,
  • director cells that sense magic, absorb magic, and cast spells,
  • an area of the brain to control all of these processes.

The magic reserve

The magic reserve is similar to adipose tissue, which stores fat. It contains numerous cells that have a vast cytoplasm filled with a few big compartments called organelles. Those organelles contained magic-binding metalloproteins (MBMPs), which are proteins that have a ring-like structural element in the centre of which one or several metal atoms are bound. Those metal atoms are what bind magic particles.   This mechanism is similar to proteins such as haemoglobin that have a ring-like haem compound in the centre of which an iron atom is bound, with the iron itself binding dioxygen molecules. MBMPs work through the same principle, but the ring structure is different, and so it is probably the result of convergent evolution rather than having evolved from haem.   MBMPs with and without magic particles bound to them are stored in the same organelles, stabilising each other. The exact ratio of MBMPs having a magic particle bound varies slightly between individual humans and can be increased with training, but it is estimated to be between 50% to 99%.
The magic reserve

The magic channels

The magic channels are extremely similar to the nerves formed by the axons of neurons, and thus scholars hypothesise that they have evolved thanks to gene duplication, a common evolutionary mechanism. According to that hypothesis, the genes forming the axons—or even part of the chromosome on which they are located—got duplicated during evolution, and one set then differentiated to specialise in the transport and control of magic rather than of neurotransmitters. Magical channels are indeed similarly formed by a myosin sheath surrounding microtubules.   Originally, different elements such as MBMPs would have been dragged along the microtubules and thus transported through the body. However, during the evolution of humans, the microtubules evolved to be covered by proteins very similar to MBMP, with different metals exposed at their surface. Those proteins form a continuous metallic network on the microtubule alongside which magic particles can "jump". This evolution considerably accelerated their transport through the body and made humans one of the best magic-using organism in nature.
Magic channel

Director cells

Director cells are specialised sensory nerve cells similar to the cells that allow for the perception of touch, heat, etc. Director cells can sense, direct, and/or absorb magic. Some cells have all three functions, while other are specialised. All of them are all located in small groups making a tight bundle in different areas of the body. The concentration of those cells is higher in some areas, thus giving them a higher sensitivity to and control of magic. This is especially the case for hands, as they are the most frequently used conduit for magic casting. The location and density of director cells can be increased by training, although major changes take a long time to occur, similar to how someone can train their non-dominant hand.
Noéline frowned at the blackboard and pinched her lips. All useless information. She had hoped better from the famous Claret university, even if it was just an introduction class. Anyone who had managed to go all the way through their schooling to here without learning the biology of the magic system was not worth the effort. She tapped her fingers impatiently on her desk, not even bothering with taking notes—the ones she had made while revising for the entrance exam were far more in depth, anyway.

Using magic


The binding of magic particles

The director cells synthesise their own MBMPs. They are brought to the internal wall of the cell membrane, where they bind to transmembrane receptors. Those receptors are proteins with sections dangling both on the internal and external sides of the membrane. When the internal section binds to an MBMP, the conformation of the receptor change, exposing a magic-binding site located on the external section of the receptor.   If enough magic is present in your environment, one of those magic particles will be able to bind to the receptor. This triggers a movement of the receptor, resulting in the magic particle moving to the internal side of the membrane. A transition protein then comes and takes the particle from the receptor and moves it to the MBMP, which is then released inside the cell.  
Mechanism magic binding protein.png
Mechanism of magic absorption and detection

Sensing magic

When the transition protein releases the magic particle, it undergoes a chemical modification and becomes "activated". This state is detected by other proteins that can then spread a signal—"magic has been detected"—to the nerves and the brain. The intensity of this signal depends on how many transition proteins are activated. This itself depends on how much magic there is in the environment, but also on how many director cells there are, and on how many MBMPs, transmembrane proteins, and transition proteins the cells synthesise. All of this is influenced by training and how sensitive to magic a person naturally is.  

To the reserve

If you are not currently using magic, once the MBMP is released with a magic particle, it is transported to a microtubule and binds to it. This triggers the release of the magic particle, which then jumps along the metal atoms at the surface of the microtubule, moving all the way through the body until it reaches the magic reserve. There, it is taken up by another MBMP. This MBMP moves inside a reserve cell where it is stored in an organelle. The first MBMP that was left behind in the director cell is degraded by the body and recycled to form more proteins as required.
Mechanism of magic sensing

From the reserve

When you are actively using magic, your MBMPs and magic particles are not transported to the magic reserve, but they instead stay in the director cells where they accumulate until they are used. A signal is also sent to the magic reserve, which then releases its own MBMPs. The magic particles they contained are transported through the microtubules until they reach the bundle of director cells where they are going to be used.   The precision of the location where the particles arrive can be increased with training. A high precision results in a higher concentration of magic that can be used and a more precise casting of the spells. Conversely, a low precision results in a leakage of magic while casting. The accumulation of magic particles inside the director cells is called the "raising" of magic.
Mechanism magic storage and use.png
Mechanism of magic storage

Casting spells

The exact mechanism by which the director cells cast spells is still under study. According to our current understanding, the MBMPs transfer their magic particles to different casting proteins, which then throw the particles outside of the body towards the target of the spell. Each casting protein gives the particles they throw a different spin and movement. The combination of different casting proteins throwing particles at the same time influences the global properties of the magic being cast, resulting in a specific spell.
Mechanism of magic casting
With nothing better to do, Noléine glanced discreetly around the classroom, though taking care to keep the façade of the attentive model student for the teacher. Her eyes stopped on the young man sitting diagonally from her. By all accounts, he was no more listening than she was, but he was more productively engaged by doing some kind of drawing.   She focused her magic in the directory cells of her eyes, using it to change the curve of her cornea to enhance her vision. Immediately, she was able to make out all the tiny details of the other student's drawing, as if she were standing with her nose right on top of the paper.   Oh.   That was an attempt at the full, detailed molecular pathway controlling magic absorption in the director cells, with well over a hundred steps of the mechanism already detailed. Nice.

Causes and symptoms of magical exhaustion

  Magical exhaustion is a condition triggered by using magic beyond the limits of one's body, thus causing potentially irreversible damages to the body. Going beyond the limits might not sound so bad. After all, we often do it with traditional physical exercise, and while it can also result in soreness or injuries, this is not regarded with the same level of alarm. The reason magical exhaustion is so dangerous is that it is associated with a mishandling of magic particles, leaving them free to wreak havoc in our body.  

Director cells and magic channels

Magical exhaustion can be caused by two main triggers. The first one is using magic for too long—until the point of exhaustion. As magic channels are used, they get worn down, and MBMPs at the surface of the microtubules get damaged. This damage accumulates and our body can only start correcting it once we stop using magic. If you instead continue to use magic and do not give your body time to recover, the damaged microtubules will prevent the smooth transport of magic particles. The particles will start to leak through the protective myosin sheath encircling the microtubules, and they will go on to wreak havoc on nearby organs.   The second potential triggers of magical exhaustion is attempting to force too much magic in the channels all at once. This will also prevent the magic particles from smoothly travelling over the microtubules. Indeed, if the particles all jump too quickly between metal atoms, some of them will not have a "landing space" free to welcome them. Those particles will also leak and damage the body. Only long-term training can alter the carrying capacity of the channels by increasing the number of microtubules in one channel, as well as the numbers and position of the channels in the body.
Mechanism organ damage.png
Mechanism of channel and organ damage

Magic reserve

The magic reserve should never be completely empty of magic particles, or the organelles storing MBMPs get unstable, resulting in a leak in their membrane and the release of their content. That sudden high concentration of MBMPs without magic particles bound is very difficult for the reserve cell to deal with, as the metal atoms are extremely chemically-reactive and can wreak havoc in the cells, killing them. If too many reserve cells are destroyed, this impairs the ability of the body to store magic. Only further training can slowly increase the size of the magic reserve back to previous levels.
Mechanism of damage to the magic reserve


Using magic triggers a lot of signalling mechanisms in the brain. During this, the neurotransmitters responsible for the signalling accumulates as leftover waste which is only cleared by sleeping. If too much waste accumulate, as it does during magical exhaustion, it interferes with normal brain function, resulting in a feeling of tiredness, headaches, pain in answer to intense magic, light and sound, a reduced ability to control magic, and difficulties in falling asleeping immediately afterwards.   In the most extreme magical exhaustion cases, magic particles can even leak in the brain and cause damage there.
Mechanism of brain damage

Long term consequences

Mild acute exhaustion is the most common form of the condition. It might result in some damage to the body, but it is unlikely to be anything that healers cannot treat. The magic system itself cannot be healed by healers and must recover on its own. It generally takes a few weeks to a few months in the case of the mild form of the condition.   Mild chronic exhaustion is defined as someone triggering mild exhaustion with a certain recurrence. The particularity of this condition is that it is sometimes so mild that individual events do not even register as an exhaustion to the individual suffering from them. Yet, damage is still done, and if they keep recurring, it can accumulate enough to create some distinct symptoms: a reduce lifespan, increased sensitivity to magic, and a reduced control over one's magic.   Severe acute exhaustion is extremely dangerous, with the level of body damage it causes often resulting in death. If the victim manages to survive, they will likely require healers' care for the rest of their life in order to mitigate the organ damage. The damage to their magic system itself is unlikely to either be repaired, preventing them from ever using magic again except in an extremely limited form. Thus, severe chronic exhaustion is not recognised as a category, as no one is able to survive long enough to trigger severe exhaustion enough times to qualify.
A woman suffering from magical exhaustion by top_ntp777396 on Vecteezy
"I want you all to take one of those rocks and pour inside it as much of your magic as you feel you safely can before reaching your limits. At Claret, you are well past the level where you cautiously groped your way towards your limits, risking magical exhaustion because of your ignorance, or weakening yourself by stopping well before your limits out of an abondance of caution. You have five minutes."   Noéline blinked dubiously at the teacher's instructions. What kind of exercise was that! Even with stopping before magical exhaustion, they would all still be completely drained for the rest of the day. Basically useless. And defenceless.   And worse, it would be immediately obvious that she had way less magic available than anyone who had passed the entrance exams of Claret ought to.   But it was not as if she had a choice.

Prevention and treatment

In order to avoid being a victim of magical exhaustion, all children are taught very young to recognise the warning signs. As the magic channels tend to be located alongside nerves, once the channels start to become damaged enough for magic particles to leak, the nerves will be the first to be hit by them, creating a tingling sensation. While starting by being extremely mild, it can quickly intensify, by which point a lot of damage will have already been made. Therefore, everyone is taught to stop immediately at the first tingling. Whether they listen or not is another question.   People also learn to estimate how much magic they can use safely, what amount of magic a given spell or ritual is going to cost them, and whether they can afford it. Although this, of course, does not prevent many from consciously going beyond their limits, thinking things will be different this time.   Treatments for magical exhaustion are rather limited beyond attempting to heal the organ damage caused by it. However, this does not mean that healers do not attempt to improve them, quite the contrary. The most promising experimental treatments focus on manually reconstructing the magic channels. The challenge in doing so rests on the fact that it is almost impossible to manipulate someone else's channels with healing magic—or other types of magic—because of how reactive the huge amount of metal atoms on their surface make them. Because of this, healers are exploring alternative methods such as cutting patients' opened or using tools like needles to interact with the channels. This has only had limited success so far.   As a reaction, people have turned their attention in another direction: inventing rituals or potions that could allow someone to go beyond their limits without suffering the consequences. No permanent solution has been found yet, but even the few hours of limitless magic use that have been achieved so far can give a massive advantage during battles—and they are indeed being put to good use by elite battle-mages. Such recipes are closely guarded by all the royal families on the planet and the most elite noble families. Nevertheless, everyone else also conduct experiments of their own to attempt to create one, seeing this as a sure way to win themselves a throne.
Listen to your teacher! by Grzegorz Rakowski on Unsplash
"Now that you are all done, partner up with someone else and use basic healing diagnostic techniques to estimate how close they are to their limits. You will then use the rock to establish what the size of their initial reserve was."   As soon as the teacher was done, Noéline hastened to stand up—without appearing to hurry, of course, that would be ungraceful—and she nonchalantly headed towards the young man she had previously noticed. He was still reluctantly putting down his pen when her presence startled him.   She addressed a pleasant smile to him. "Would you like to partner up with me?"

Population affected


People at risk

Almost everyone will get magical exhaustion at some point during their childhood, as it is difficult for children to judge their limits—or to respect them—and they still need to learn the wisdom of listening to their elders and mentors.   Soldiers are particularly at risk. In fact, it is considered inevitable that, during a battle, almost all of the combatants will end up with some form of magical exhaustion if they survive. This is for two reasons. First, with the adrenaline and the potential injuries, it is almost impossible for anyone to actually pay attention to the tingling warning, or even to the much worse pain caused by strong damage to the magic system. Second, even if they in fact hear the warning, few soldiers will bother to listen. Indeed, having an intact magic system will not do them a lot of good if they end up dying because they could not muster a little more magic to shield themselves.   The other category of individuals most affected by magical exhaustion is students. This is because many of them are likely to have an unhealthy lifestyle, and the lack of sleep and potential alcohol and drug abuse does not make feeling the warning signs easier. In addition, students are very often pushed to their limits by their studies, both in class and during last-minute revision before exams.
A sword-wielder mage from the South by Some Tale on Unsplash


Individuals with troubles hearing and interpreting the signals sent from their body are, of course, less likely to stop using magic in time to avoid exhaustion. Some other individuals, especially those with chronic pain, have a dysregulation in the sensory processing of their brain, which leads the signal sent by their body to be amplified or muffled. This results in them thinking that they have already reached their limits even when it is not the case, or, more dangerously, in them not realising they have already reached them.
Characters challenges magical university.jpg
Lidéric frowned, eyes closed, his fingers on the top of Noéline's sternum and her rock in his other hand. When he looked back at her, she was ready to welcome his suspicion with a fakely half-awkward, half-annoyed smile and laugh.   "I'm afraid I had the great idea of over exerting myself this morning redecorating my apartment. Which was a much more productive use of magic than what we are currently doing, anyway."   Lidéric's face immediately cleared, for, of course, who would even think that she would have been able to trick her way past Claret's power-level entrance tests?   When they exchange position, Noéline had to suppress a scoff at the way his rock radiating an enormous amount of magic. There had clearly been no doubt about him getting admitted.

Social impact


People view on those afflicted

Since everyone does end up getting magical exhaustion at some point in their childhood, people tend to view this as a rite of passage—although one that needs to be handled carefully to ensure that the children survive it with their magic system intact. Once children reach their teenage years, however, that indulgence fades, and getting magically exhausted is seen as a lack of maturity and self-control. It is even more shameful in adults and leads to social ridicule, unless it can be excused by a war or a life-threatening incident.

Legends of famous people

Despite this taboo aspect in older people, magical exhaustion has a special place in history and legends. Those almost always include a section where the hero has to choose to make the ultimate sacrifice by going through magical exhaustion and continuing to use their magic despite feeling their body fail apart all along, until they either reach death or are forced to live heavily disabled and magicless. Alternatively, the stories will feature some extraordinary individuals who have managed to find a permanent way to go beyond their limits without suffering magical exhaustion, either as part of their quest to defeat evil, as a prize for it, or as an epiphany or revelation coming to them during the final battle.

Place in training

Any competent teacher will take care to protect their pupils from risks of magical exhaustion. Unfortunately, not all teachers are competent. Worse, a small number of teachers actively incite their pupils to reach magical exhaustion. There are several reasons behind this: 1) a form of child abuse, 2) a form of sabotage of the students with the teacher being paid a bribe by an enemy family, or 3) the teacher being part of a group believing a long-debunked theory stating that reaching a state of magical exhaustion is necessary to enhance growth of the magic reserve.   In addition, there is intense traffic of enhancing treatments that are supposed to help those who ingest them go beyond their limits without suffering from exhaustion. Sellers are most often scammers, but they can also be the scientists attempting to invent those treatments and wanting to get guinea pigs to test them, or, even more rarely, the employees of the noble families owning the real recipes for those treatments. The small possibility of being able to acquire the real deal is what pushes many to take fake treatments out of naivety or trust in the wrong person.


Because of how dangerous magical exhaustion is, the circumstances leading to it are strictly regulated. According to the laws, all cases must be investigated to determine whether the authority figures present during the events or having had the possibility to influence the sufferers previously are at fault. Since adults suffering from magical exhaustion will often attempt to present themselves as victims of bad influences to avoid the social stigma resulting from their stupidity and lack of self-control, all investigations must be throughout to avoid miscarriages of justice.   Despite forcing people to go beyond their limits being also illegal during military training, the laws regulating magical exhaustion in the army are more ambiguous. This is because going through exhaustion can sometimes be a necessary sacrifice to avoid outright deaths. The latest famous case occurred ten years ago during the war with Nitra. This was an attempt from soldiers to have their superior officer condemned for having forced them into an attack despite them having already reached their limits. It was judged that this breakthrough was the only reason the battalion survived, and so the officer was exonerated.
"So," Lidéric whispered to her as their teacher went on about magic recovery, "do you want to join me at the library afterwards to do our project together?"   Noéline smirked and mumbled, "It'll be a pleasure. Seems like we need to raise the level of this class all by ourselves if we don't want to die of boredom."   He snorted. "Don't get your hopes too high. I heard there were a few too many prominent cases of magic exhaustion last year, and the court is putting pressure on Claret so that it doesn't happen again."   Noéline winced. "Oh god. I hope we're not going to get our education curtailed because of a bunch of idiots who don't know their limits at our age."   Lidéric nodded vigorously. "Thankfully, the prince is still attending Claret with us. I doubt he will allow this nonsense to go on for much longer."   Noéline sent him a curious side glance while still pretending to be listening attentively to the lecture. She would not have expected the prince to have that much influence over the court, given that he was from a side branch of the royal family. But she had recognised Lidéric's family name. They were very prominent political players, and he would know what he was talking about. While she had no political ambitions herself, she could not deny a certain curiosity about the topic. It seemed that Lidéric would make an interesting friend for more than one reason.

What to read next


Cover image: A woman suffering from magical exhaustion by top_ntp777396 on Vecteezy


Author's Notes

  Please don't hesitate to point out in the comments anything that is unclear! The goal with this world is to show the sciences and classes the characters follow, but I still want the articles to be understandable to any reader :D

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17 May, 2022 19:52

I always love how scientifically you explain magic and things. It makes diving into your worlds such a pleasure. Great article - I really like all the diagrams! :D

Eternal Sage AmélieIS
Amélie I. S. Debruyne
17 May, 2022 21:04

Thanks :D Being able to talk about proteins was a pleasure XD I'm finally making a good use of my PhD! XD

To see what I am up to, here is my civilisation challenge article.
17 May, 2022 21:45

This is both fantastic and inspiring! Makes me want to go deeper into my own system. Well done! <3

Snarky and Sarcastic to the End
Eternal Sage AmélieIS
Amélie I. S. Debruyne
18 May, 2022 07:47

Thanks :D It was really fun to make, even if I'm not sure how much I'll be able to feature in the actual novels XD

To see what I am up to, here is my civilisation challenge article.
18 May, 2022 06:30

Wow. What a complex and detailed system! It seems from the article that since magic particles are bound to metaloproteins that specific metals will have magic redirection or capturing properties. (Much as oxygen with catalysts produces rust in iron or causes staining of silver). Likewise I'd imagine a therapy for exhaustion might be a diving bell/ magical pressure chamber that provides a magically enriched atmosphere. The article gives such an interesting underlying biology that it also implies that there might be magically active/ sensitive plants performing a haeme like duplication with chlorophil.

Eternal Sage AmélieIS
Amélie I. S. Debruyne
18 May, 2022 07:59

Thank you for your comment :D   Yes, different metals will have different magic-binding properties. I haven't yet decided everything about that, but I think I'll have to make an article about it at some point.   And yes, plants will also have an equivalent magic system though I have not yet think about how it's going to be. I might mix things up a bit to make it different from humans XD   A pressure chamber without any magic inside is an interesting idea. People would have to be isolated from magic while they recover enough. And then, they could have the opposite, a chamber with a high magic pressure to allow people who are simply tired to replenish their reserve more quickly. Though both would only be a solution for rich people. Everyone else would simply have to find magic currents with more or less magic.

To see what I am up to, here is my civilisation challenge article.
18 May, 2022 12:38

Incredible detail and inner consistency! It also sparks all kinds of questions. How does one "train" magic capacity? Is it like training VO2 max? Can you synthesize MBMPs to make magic artifacts? Are there diseases similar to MS where the myosin sheath breaks down? Magical diseases could be pretty wild! One note, you mention "genuine pigs" but I think you meant "guinea pigs." This world is really fun!

Eternal Sage AmélieIS
Amélie I. S. Debruyne
19 May, 2022 07:43

Thanks for the comment :D   Yes, training magic is like training for VO2 max. It's an intense and slow process to not make things any easier for people :p And also, you can't really go higher than a certain limits, that limits depending on individual.   Noéline, for example, will never have a very big magic reserve, but she can influence the number of magic channels that she has and their locations. And her magic sensitivity is super high and she has a high control on her magic - the precision in her spells that this gives her is how she "cheated" her way through the entrance exams, by doing something that only people with a big reserve are supposed to be able to do.   People are not synthetizing MBMPs. They mostly use the pure forms of metal, alloys, or some other matter with bits of metal sprinkled in them. Although I imagine that taking the magic channel from a corpse would be very popular with some people - and since only humans and no other animals have them...   There should definitely be diseases like MS! Lots of fun diseases to compensate for the fact that healing magic can solve a lot of ailments that we can't with our own technologies.   And thanks for noticing the guinea pigs!

To see what I am up to, here is my civilisation challenge article.
26 May, 2022 13:56

I absolutely love all the diagrams. I typically try to ignore typos, but I think your title might have one :)

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Eternal Sage AmélieIS
Amélie I. S. Debruyne
28 May, 2022 09:46

Thanks! I had fun making all of those diagrams XD And thank you for pointing out that typo! I made a last minute change with the title and I didn't notice that my French slipped in...

To see what I am up to, here is my civilisation challenge article.
31 May, 2022 07:00

Really interesting and detailed - as always :)

Author of the Wyrd West Chronicles and the Toy Soldier Saga. Mother of Bunnies, Eater of Pickles, Friend of Nerds, First of her Name.
Eternal Sage AmélieIS
Amélie I. S. Debruyne
2 Jun, 2022 12:08

Thank you :D

To see what I am up to, here is my civilisation challenge article.
18 Aug, 2022 18:13

Love all the details! Made me feel like I was reading a textbox so you excelled at doing that! The images are very clear and I loved all the biology terms in the text. Makes me miss learning about biology

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Love to code, but this one is driving me crazy!
Hey look, I have a SC prep article
Eternal Sage AmélieIS
Amélie I. S. Debruyne
19 Aug, 2022 07:27

Thanks :D I'm glad it wasn't too boring XD

To see what I am up to, here is my civilisation challenge article.
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