This is going to take some explaining, but the basic idea is thus:

In the world I'm creating, if matter is exposed to enough magical energy it ceases to respect the laws of physics and becomes known as "eldritch matter."

Eldritch matter vaguely retains it's original shape and but on a microscopic level it's essentially a solid with the properties of a liquid (and floats) that retains a shape at a general level, but no complex structures are able to be maintained as the matter constantly shifts.

There are some animals that have become eldritch matter, and when they do they survive, and become and eldritch entity, a creature that defies the laws of physics but in return has no neurological function because their neurons are not able to be maintained, so they are essentially reduced to the lowest form of intelligence possible, a mindless beast that does nothing but endlessly seek magical sources to suck dry to maintain it's existence.

Since they are essentially immortal so long as more magical sources can be found, people have tried multiple times to become eldritch matter, the basic idea being maintain the structures of the brain while all else becomes eldritch matter. This almost never works, as eldritch matter tends to spread, but one person has achieved it.

They now take the form of an amorphous mass that has been crafted to resemble their previous form, but their brain structure has been maintained so they can retain control over it. However, over time their neurons very slowly turned into eldritch matter, destroying the structure and sending them essentially mad.

This is (very roughly) equivalent to a neurodegenerative disease, as parts of the brain slowly become useless, but it would be attacking every part of the brain at once, albeit extremely slowly and from the outside. I was wondering what irl disease is the closest equivalent so I can model their behaviour on that of sufferers of that disease?

p.s. i have no basis to know if any of this is correct or plausible

  • $\begingroup$ Gain of function is more interesting for a fiction than loss of function. I can only lose what I have, and then I have less. But there are an infinity of things I don't have, and might acquire. $\endgroup$
    – Willk
    Jul 30, 2020 at 22:23
  • $\begingroup$ If the eldritch animals have no neurological function, how are they able to seek out magical sources? Even the "dumbest" seeking behavior requires some kind of driving mechanism, (i.e. intelligence). $\endgroup$
    – cowlinator
    Jul 30, 2020 at 23:16
  • $\begingroup$ @cowlinator they have essentially the form of intelligence bacteria does, they can sense magical sources and generally head in the direction with more of it $\endgroup$ Jul 31, 2020 at 4:21
  • $\begingroup$ @Willk you gain a great deal of functions, including the ability to freely manipulate the shape of your body and matter, the ability to completely defy physics (i.e. float) and the aforementioned immortality $\endgroup$ Jul 31, 2020 at 4:24
  • $\begingroup$ I think the short answer is Death. If your brain cells change their topology the result is to that function those cells governed. If you want examples of what happens when pieces of the brain are irrevocably damaged due to disease, read 'The Man who mistook his wife for a hat.' It provides fantastic insight into how fragile our grey matter is $\endgroup$
    – EDL
    Jul 31, 2020 at 21:53

4 Answers 4


The affected person would die long before neurodegeneration begins.

The human body depends on the harmonious interaction of many different complex systems and intricate organs. If the lower portion of the human body is affected before their brain, many of these vital processes would quickly cease to function, resulting in death.

Take the circulatory system, for example. Suppose just one of a human’s appendages is affected by this “eldritch disease.” All of the blood cells that flow through this appendage will lose their structure and be lost. Thus, the brain will quickly run out of oxygen and die.

  • $\begingroup$ the idea of eldritch matter is that because it has a loose structure it can become any substance, providing someone can control it. This would require a lot of knowledge about chemical composition, but someone who can consciously control eldritch matter can turn any other eldritch matter into any substance. $\endgroup$ Jul 31, 2020 at 4:28

I'm going to assume that, since the rest of the body is Eldritch Matter, the rest of the life functions are somehow intact and the brain can survive in its current configuration.

Neurodegenerative diseases (ND) are typically categorized by the damage to the brain, but usually not in the way we're discussing here. As opposed to actually destroying and removing brain cells, NDs typically involve some kind of protein growth that renders the cell communications useless in some way or physical damages them to the point that they no longer communicate. This should effectively be the same thing as removal of the cells, though, so this an adequate starting place.

The most fitting ND subtype would be Alzheimer's Disease (AD). AD is associated with formations occurring in the brain that damage it and cause it to atrophy. Unilateral brain atrophy might be the most similar to the slow-brain-destruction scenario you've expressed, and thus this seems fitting. This disease progresses somewhat slowly, with the common expectancy being 3 to 9 years. That's slow enough for the changes to occur in a timeline wherein this character is still viable, but almost demonstrably being affected by the loss of brain tissue. Various early symptoms include reduction of short-term memory and learning capacities, loss of vocabulary, and a decrease in word fluency. Mid-term symptoms can include increased language deficit, irritability, episodes of uncontrolled laughing or crying, outbursts of aggression, and resistance to care. The late stages do seem to reflect the other entities you mentioned, where the brain structures associated with higher-function are completely destroyed and the Eldritch Matter takes over, so to speak.

Of course, there are other physical symptoms, but the Eldritch matter appears to be responsible for physical actions in this case and I'm going to handwave and assume that the brain can communicate with that matter as long as it is conscious and capable of higher thought. Which does raise an interesting question, what happens if this character "falls asleep" or becomes unconscious for a period?

  • $\begingroup$ I imagine when sleeping the matter would naturally coalesce into a smaller form, albeit with the mixed pieces of various eldritch matter somewhat maintaining a form within the ball, coming together in a rather terrifying visage. Eldritch beings usually have the ability to maintain their form and this would probably be more of an unconscious process than a conscious one, other wise operating would be a nightmare. Thank you, this was very helpful! $\endgroup$ Jul 31, 2020 at 18:29

Closest real neurological disorder to the state of being an eldritch entity?

There are some animals that have become eldritch matter, and when they do they survive (...)

Ok, so far so good.

(...), and become and eldritch entity, a creature that defies the laws of physics but in return has no neurological function because their neurons are not able to be maintained (...)

If the animal is a sponge or a member of the placozoa phylum, then it becomes a super version of itself. Any other kind of animals becomes a dead animal. Even simple animals such as jellyfish depend on having a huge amount of neural connections (not simply many neurons) in order to function.

Then you mention a human that survived, but:

over time their neurons very slowly turned into eldritch matter, destroying the structure and sending them essentially mad.

Alzheimer, Parkinson, Huntington, ALS and Batten destroy specific parts of the brain. For a more generalized and homogeneous form of slow destruction, you're looking for spongiform encephalopathy. A very well known disease of this kind is Kuru:

Kuru is a very rare, incurable and fatal neurodegenerative disorder that was formerly common among the Fore people of Papua New Guinea. Kuru is a form of transmissible spongiform encephalopathy (TSE) caused by the transmission of abnormally folded proteins (prion proteins), which leads to symptoms such as tremors and loss of coordination from neurodegeneration.

The preclinical or asymptomatic phase, also called the incubation period, averages 10–13 years, but can be as short as five and has been estimated to last as long as 50 years or more after initial exposure.

The clinical stage, which begins at the first onset of symptoms, lasts an average of 12 months. The clinical progression of kuru is divided into three specific stages: the ambulant, sedentary and terminal stages. While there is some variation in these stages between individuals, they are highly conserved among the affected population. Before the onset of clinical symptoms, an individual can also present with prodromal symptoms including headache and joint pain in the legs.

In the first (ambulant) stage, the infected individual may exhibit unsteady stance and gait, decreased muscle control, tremors, difficulty pronouncing words (dysarthria), and titubation. This stage is named the ambulant because the individual is still able to walk around despite symptoms.

In the second (sedentary) stage, the infected individual is incapable of walking without support and suffers ataxia and severe tremors. Furthermore, the individual shows signs of emotional instability and depression, yet exhibits uncontrolled and sporadic laughter. Despite the other neurological symptoms, tendon reflexes are still intact at this stage of the disease.

In the third and final (terminal) stage, the infected individual's existing symptoms, like ataxia, progress to the point where they are no longer capable of sitting without support. New symptoms also emerge: the individual develops dysphagia, or difficulty swallowing, which can lead to severe malnutrition. They may also become incontinent, lose the ability or will to speak and become unresponsive to their surroundings, despite maintaining consciousness. Towards the end of the terminal stage, patients often develop chronic ulcerated wounds that can be easily infected. An infected person usually dies within three months to two years after the first terminal stage symptoms, often because of pneumonia or infection.

You can taylor your eldritch scrapies to last a shorter or longer time on your character as you wish.


Alzheimer's is characterized by the degeneration of gray matter (the outermost layer of your brain); so, by the time you get that far, those will be the symptoms you observe... that said, our behaviors are not guided by our brain alone. While our brain is where the thinking happens, most of what we feel comes from our endocrine system. You Adrenal glands are located by your kidneys, your thyroid is in your lower throat, your genitalia are located... well you know...

So with these organs rendered useless, your subject matter will have several other significant complications from the moment he first pulls off his experiment. Even with most of your physical body made immortal, you'd still feel the neurological effects of improperly working glands such as:

Hypocortisolism: Confusion, psychosis, slurred speech, severe lethargy, and difficulty remaining conscious.

Hypothyroidism: Fatigue, Feeling cold, Decreased memory and concentration, ad Abnormal sensation (which might be intensified by the fact your body's been turned into jelly).

Castration: Lack of sex drive and reduced aggression.

By in large, your person will never be able to think straight even with a fully preserved brain, because the systems that keep you awake and active will all be compromised.

A different perspective might help?

Frankly these side effect are so bad even after hand waving away the instant death issues that, I would like to propose something very different which might get you a mental disorder without scrambling your brain at all. If eldritchism were explained by a warping of your underlying reality, then your body and mind could continue to function normally with blood and neurons all doing what they do in your own reference point, but flexing your reality would from your point of view flex everything around you which would be extremely disorienting. We humans learn things like balance and proprioception through conditioned observations. We know this because of experiments which have shown that people who wear visors that flip or distort images can be acclimated to, but once you do, normal vision becomes harder to navigate.

Your flexible immortals in this case do not go dumb per se, they just stop being able to understand what they are seeing and feeling as their bodies constantly shift and change. They will need to work very hard to keep their reality in familiar shapes but over a relatively short period of time, finding what is familiar will get harder and harder as your brain tries to constantly adapt to the unpredictable nature of your new senses. The only thing they are able to understand after awhile is magic because it is already formless and therefore just as easy to see and interact with regardless of your perceptions.

So, your hero? May have instead of stabilizing his brain, learned to stabilize his eyes and ears, and his deterioration could begin as small distortions in his perception like having astigmatism that gets exponentially worse over time. After a while shapes will become harder and harder to make since of resulting in something more like really severe dyslexia or visual agnosia until finally your world just descends into totally nonsensical perception like static.


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