I'm currently trying to plot out a novel, the sequel to my Salamander and Brothers. Part of the plot involves a succession struggle. I mention in one of the previous books, set about fifteen years later, that the king took six months to die, so I need a disease that would be incurable but slow acting.

The books are fantasies in a world that is mostly like our world but with physics sufficiently different to include magic, a craft for centuries currently becoming a science. Ordinary medicine is at something like an 18th century level, so no antibiotics and no clear understanding of the nature of disease. They do, however, have magical healers. Healers have, in effect, X-ray vision, plus some ability to affect what they see, details depending on talents and training — some healers, for example, can close a wound by weaving back together the flesh. They have a very good understanding of gross anatomy, no understanding of anything at the cellular level. One very skilled healer in a previous book knows that blood has to circulate but does not know what it actually does. I don't entirely know myself, since the different physics may to some degree result in different biology. It's pretty clearly the case, although not widely realized, that all living things have some amount of magic which is in some way connected to their life.

It follows from all this that when the king, who has access to good healers, gets sick, they cannot cure him but may be able to use their abilities to ameliorate symptoms, close up sores, say. I could invent a disease but would rather use a real one, and since I don't know much about diseases I thought I would see if someone else here did and could offer a suggestion. It has to be something that would plausibly kill slowly, cannot be cured without modern medicine, ideally where the symptoms can be reduced by healers. One possibility is syphilis, which would introduce some additional plot elements, possibly but not necessarily useful, but my impression is that, treated with 18th c. medicine (mercury), it was a pretty slow killer. Tuberculosis also occurred to me.

One additional possibility. It could be that the disease is one that can kill, hence is generally believed to have killed him, but that what actually happened was that he was holding steady, with the disease not cured but symptoms held down by healers to a non-lethal level, and was actually killed by poison. _

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    $\begingroup$ You do realise, you already mentioned one: syphilis treated with mercury. The insanity would appear to be caused by syphilis, but actually be the result of heavy metal poisoning--just mess up the dose or mixture $\endgroup$
    – nzaman
    Commented Jan 27, 2021 at 5:35
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    $\begingroup$ The king is morbidly obese like weighting half a ton, then six months later he died of cardiac arrest and as for the magic healers they really just offering non contact massages all this time to their king ;D $\endgroup$
    – user6760
    Commented Jan 27, 2021 at 8:39
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    $\begingroup$ Cancer. Many fictions have this as something magical healing can't fix. The healers might be able to extend his life and make him more comfortable, though. $\endgroup$
    – NomadMaker
    Commented Jan 27, 2021 at 9:13
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    $\begingroup$ When you are writing a fantasy story, then why not just invent a disease with the properties you need? $\endgroup$
    – Philipp
    Commented Jan 27, 2021 at 10:29
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    $\begingroup$ Seems like it might be useful to have a disease that readers can recognize without naming it. Cancer would probably work, or TB. Also, seems like the x-ray healers might have mapped out the circulation of blood historically? $\endgroup$
    – Ms Jy
    Commented Jan 28, 2021 at 18:07

10 Answers 10



Leukemia if the king is young, colorectal cancer if the king is older. If the magical healers can't affect cellular division, excising tumours would only slow things down, and would probably be too late.

As a bonus, non-communicable, so no one around the king (say, his sexual partners, in the syphilis case) gets ill - just him.

  • $\begingroup$ This. Just like the bodies natural defenses cannot differentiate between healthy and cancer cells, the magic won't be able to either. $\endgroup$
    – Hobbamok
    Commented Jan 27, 2021 at 14:09
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    $\begingroup$ @Hobbamok: That's somewhat post-hoc logic. Quite a few unhealthy cells are recognized and killed off early. We just use the word cancer for those that have beaten the immune system. $\endgroup$
    – MSalters
    Commented Jan 27, 2021 at 14:54
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    $\begingroup$ Melanoma. Has the advantage it can mysteriously grow into a curséd symbol. Plus it's terrifying. "Oh look not noticed that mole before? Oh, now I'm dead" $\endgroup$ Commented Jan 27, 2021 at 15:04
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    $\begingroup$ This was exactly my thought. Excising the tumors at a macro level would likely leave behind some cancerous cells, which of course would replicate and eventually metastasize, but could extend his life and ameliorate symptoms at least for a while. Even though the healers might not understand cancer per se, they would still see cancerous masses and be able to realize that healthy people don't have them. $\endgroup$
    – Doktor J
    Commented Jan 27, 2021 at 15:08
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    $\begingroup$ In one of my fantasy stories which had cancer the healing magic stimulated regeneration and cell division. Which not surprisingly when used on those with cancer caused it to accelerate not decelerate. As such the solution was to use death magic to kill the cancer (which kind of had the same side affects as chemo). $\endgroup$
    – Anketam
    Commented Jan 27, 2021 at 15:38

An autoimmune disease.

This is a category of diseases where the body misidentifies some of its own cells or parts as harmful viruses, and tries to get rid of them, essentially attacking itself in the process. Frankly these are still not well understood today, but a correlation has been suggested with cleanliness: the idea being that if you live in clean spaces all your life, your immune system never comes into contact with actual harmful bodies, and is more likely to misidentify its own bodies as harmful and attack them.

Infections would be the hardest kind of disease for your healer to resolve, so a king intent on living a long time would be compelled to adopt a very clean lifestyle. He could even have commissioned spells to be created to disinfect his rooms and food, and doom himself in the process. You can play around with the idea a bit; if you always use magic for healing, then the body may develop an equivalent disease when it is not doing what the magic is doing for it.

But if you want a specific example: one autoimmune disease, lupus, is very tricksy. The healthy cells being targeted can be of any kind, so this is still very hard to conclusively diagnose today. The disease takes years to kill a person but the early symptoms are very generic and easily missed. They include fever, malaise, joint pains, muscle pains, headaches and fatigue. All of those can be alleviated even with non-magical herbal medicine.

A more distinctive symptom is rash on the cheeks. But the effect may be subtle and the king could just cover it up with make-up. Other possible symptoms (don't occur in all patients) are hair loss and Raynaud syndrome, fingers discolouring when cold.

In the long term, a patient suffering from lupus will develop real infections and organ failure. Then the symptoms and prognosis depend on what organ goes out first. If the liver fails your king will turn yellow and die in months or weeks. But the first stages are so easily missed that I think this could work for your scenario.

  • $\begingroup$ Good answer. Just out of curious interest, could you cite a source for the suggested correlation between autoimmune disease and over cleanliness ? $\endgroup$
    – Hoki
    Commented Jan 28, 2021 at 10:24
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    $\begingroup$ @Hoki Sure; the broader correlation between cleanliness (particularly in childhood) and compromised immune system is called the hygiene hypothesis. One article about autoimmune in particular: Okada et al. $\endgroup$
    – KeizerHarm
    Commented Jan 28, 2021 at 10:55
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    $\begingroup$ I'm just going to drop this in: some are theorizing that parasites could possibly alleviate the issues explained by the hygiene hypothesis. Give everyone a tape worm that isn't deadly, and the body will spend its days attacking it instead of itself. $\endgroup$
    – Bobort
    Commented Jan 28, 2021 at 15:52

Frame Challenge: It's Not A Disease!

No, no, the king died from a curse. You mentioned a succession struggle, yes? Curses are ideal for this; if the healers can only deal with living things, they'll be helpless against dark magic (but trying their best to increase the king's lifespan).

Since darkness is an element of mystery, the healers might not even know they're dealing with a curse; they might think it's just a baffling disease. The would-be successor (read: usurper) would likely the one who cursed him, or rather gained the means to curse him from a mysterious figure and/or being.

But why would this mysterious character help him? Perhaps he's not; perhaps the usurper is just a pawn in his "benefactor"'s quest to finally take the throne, or perhaps this character is aiding the usurper's rise to power because he can control him, allowing the man on the throne to be targeted for his monarchial actions. In essence, the helper will be the one in charge; the usurper will just be a figurehead.

Or perhaps the one who cursed him doesn't care who takes the throne; they just want revenge against the king. In this case, it'd be someone he wronged (someone who can say to the king "You took everything from me!") and ends up being killed by. In this case, I think the curse would be leeching away the king's very essence....think "You took everything from me, so I'm taking everything from you!"

Now, the wronged party may be satisfied with absorbing the king's very soul, but then again, he may not. Perhaps he or she wants to be the man or woman in charge, with all the power, all the gold....it's a distinct possibility. The wronged party may even have to fight against the rightful successor and the scheming, would-be usurper, creating the power struggle you so desire.

The wronged party could even be more moral than the king, or desire to put a more moral person (themself) in charge. Perhaps they only wanted revenge, they didn't realize that they had been given a lethal curse instead of a tormenting spell.

In the end, it's your call, but I hope this helps.



Your king got a splinter that became infected, and the infection got into the bloodstream.

This has been killing people for millennia, and still with modern medicine the odds of survival are around 50%.

Usually sepsis is much faster acting but your army of healers keep repairing the damage, but not treating the underlying infection.


You could try: Genetic Prion Disease

In the context of your story, these are diseases that would onset later in life, presumably after a king has already ruled for a time. There would be few if any symptoms early in life and then they would suddenly present with worsening cognitive difficulties, challenges with balance, and jerking movements. It would progress to difficulties walking, speaking, worsening depression, agitated psychosis, and possibly seizures. There is a variant called familial fatal insomnia that would have the insomnia present in the name. Eventually he would probably pass when his muscles fail, he is unable to breath and his heart stops beating from lack of oxygen.

Your healers would not be able to see anything, because even with our advanced imaging we often don't see anything. The problem is from misfolded proteins at the molecular level. There is no gross abnormality of the brain or other organ systems visible from the surface or able to be found using Xrays, MRIs, CT, ultrasounds.

They would be able to treat some of the associated symptoms, but it would not have any impact at all on the disease itself. Herbs for pain and low dose paralytics or muscle relaxants would work for muscle spasms and jerks, maybe the seizures when they manifest. Psychosis is likely hard to treat except by "soothing" or sedating him to the point where he is no longer bothered from the illusions and delusions from the psychosis. Soothing may also be helpful for the mood issues, which often present as anxiety or depression.

Most variants fit your "6 month" timeline perfectly.

The disease follows an autosomal dominant inheritance pattern which means that it runs in families and a child that has an affected parent would have a 50% chance of getting the disease as an adult. There would be the possibility of revealing infidelity significantly after the fact by having a child that has the disease when neither parent did have it (which would be practically impossible).

Given that it is inheritable with variability in how long it takes to progress from mild cognitive impairment (which may not be readily apparent to observers) to progressive severe disease, you also have the possibility of having an aristocracy where it is not uncommon for individuals in power to literally fall mad. Strange behaviour would then cause significant stress on everyone due to the uncertainty of whether an individual has had a sudden change of heart, is being progressive, radical, or is literally going crazy.

People can become quite aggressive during psychotic episodes with delusions that something is true which is demonstrably false, or hallucinations of things being present that nobody else can see. I'm sure can be integrated without too much imagination.

Wow that is depressing.

From GeneReviews, which is a reliable source for clinical information on these diseases:

Genetic prion disease generally manifests with cognitive difficulties, ataxia, and myoclonus (abrupt jerking movements of muscle groups and/or entire limbs). The order of appearance and/or predominance of these features and other associated neurologic and psychiatric findings vary. The three major phenotypes of genetic prion disease are genetic Creutzfeldt-Jakob disease (gCJD), fatal familial insomnia (FFI), and Gerstmann-Sträussler-Scheinker (GSS) syndrome. Although these phenotypes display overlapping clinical and pathologic features, recognition of these phenotypes can be useful when providing affected individuals and their families with information about the expected clinical course. The age at onset typically ranges from ages 50 to 60 years. The disease course ranges from a few months in gCJD and FFI to a few (up to 4, and in rare cases up to 10) years in GSS syndrome.

The advanced disease stage is characterized by rapid involuntary muscle jerks (myoclonus), muscle stiffness (either rigidity or spasticity), and ataxia. The median survival following disease onset is six months.

  • $\begingroup$ Familiar fatal insomnia was actually the disease Paul LeBlanc in the tv show Next had. While I don’t know how accurate that depiction was, symptoms included extreme paranoia and hallucinations which would play well into a future power struggle. The king in his last few months would be acting increasingly paranoid causing those who might succeed him to then distrust each other, not realizing that it was actually just a result of the disease that had been plaguing the now dead king. $\endgroup$
    – user64742
    Commented Jan 29, 2021 at 5:20

Mercury Poisoning

A single exposure to a small amount of an organic mercury compound can be fatal in around that time frame (note: metallic mercury is not easily absorbed by the body and would not work).

What happens is that the mercury bonds with selenium in the body, which is part of some key enzymes necessary for repairing damages to the neural system. When they stop working, the neural system eventually breaks down.

Citing from the tragic real world fate of Prof. Karen Wetterhahn:

Wetterhahn would recall that she had spilled several drops of dimethylmercury from the tip of a pipette onto her latex-gloved hand. Not believing herself in any immediate danger, as she was taking all recommended precautions, she proceeded to clean up the area prior to removing her protective clothing. However, tests later revealed that dimethylmercury can, in fact, rapidly permeate different kinds of latex gloves and enter the skin within about 15 seconds.

Approximately three months after the initial accident Wetterhahn began experiencing brief episodes of abdominal discomfort and noted significant weight loss. The more distinctive neurological symptoms of mercury poisoning, including loss of balance and slurred speech, appeared in January 1997, five months after the accident.

Wetterhahn was removed from life support and died on June 8, 1997, less than a year after her initial exposure.

  • $\begingroup$ Are there likely to be organic mercury compounds in a pre-modern, roughly English 17th-18th century, society? $\endgroup$ Commented Jan 28, 2021 at 21:20
  • $\begingroup$ @DavidFriedman, alchemists were fascinated with mercury, and found all sorts of exciting ways to give themselves mercury poisoning. $\endgroup$
    – Mark
    Commented Jan 28, 2021 at 21:43
  • $\begingroup$ @DavidFriedman: I don't know chemistry nearly well enough to say whether an early modern alchemist could realistically synthesize an organic mercury compound, but it seems at lease close enough to possible to handwave, it's not like an atomic bomb where you need an industrial-scale enrichment process. $\endgroup$ Commented Jan 29, 2021 at 10:05
  • $\begingroup$ "metallic mercury is not easily absorbed" Ah, that explains why I am still alive. As a 12yr old I used to go into town and buy liquid mercury over the counter from the pharmacy - yes this was before these days of health-and-safety. I would take it home and invent games with it including running it from one hand to the other. Nobody ever told me of any dangers. I still wonder if it damaged my memory. I'm retired now and people expect my memory to be bad but, all through school I had trouble memorising anything. I did have quite a lot of digestive troubles also. Luckily no swallowing! $\endgroup$ Commented Jan 29, 2021 at 20:53

Arsenic poisoning, whether deliberate or accidental.

If accidental, the king may be drinking water, specifically reserved for him from a newly discovered spring or well that is naturally contaminated by very high levels of arsenic.

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    $\begingroup$ Wikipedia says: "The toxicity of arsenic has been described as far back as 1500 BC in the Ebers papyrus." So, thinking that healers might be able to recognize the king's disease as a poisoning? $\endgroup$
    – Ms Jy
    Commented Jan 28, 2021 at 18:19

Pancreatic cancer

Even with modern medicine, this is something you are unlikely to survive as it usually shows no symptoms until it is very advanced. Six months is quite plausible.


A combination of age related diseases

It's exactly this that happened to Timo Sarpaneva, a famous Finnish designer. His state started with vascular dementia but he also got Alzheimer's and Lewy Body disease on top of that.

In his case, especially the last year was difficult based on a documentary I saw so I imagine you could scale that to half a year.

It would be a natural option especially if the king is old.


18th century medicine?


AKA the White Death. On the one hand, people in dry climates have been known to last for years with TB. On the other hand, a 1994 study in Baltimore had time to death for those who died (most survived) of 39 days. These were generally immuno-compromised, but the two numbers bracket 6 months pretty well.


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