A very common trope in fiction is the concept of some powerful, forbidden spell/martial art/etc., which is said to have a cost paid in the user's lifespan. Now, oftentimes this literally physically ages the user, but not all the time. When Tien uses this sort of life-force-draining ability in the anime Dragonball Z, for example, over-using it just causes him to collapse and die, still as young as he was before he used it, just dead.

Now, this can obviously be attributed to the magic system of these settings having "life force" as a physical, finite resource that you will eventually run out of, but suppose your setting doesn't allow for that, whether because you're more grounded in realism, or that just isn't compatible with the magic system of your setting. That would mean that this ability would be doing something to the body that will cause you to die younger and younger the more you use it, until eventually over-use will kill you outright.

If the setting's mechanics of life and death were completely grounded in realism, what could this ability be doing to the body that would reliably lower the age you could realistically live to while doing as little to your overall health as possible before it reaches that stage?

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    $\begingroup$ "Completely grounded in realism" meaning something happening in real life, (like carcinogenic effect of smoking), or something that is only scientifically plausible (like stripping telomeres from all chromosomes)? $\endgroup$
    – Alexander
    Oct 4, 2021 at 21:26
  • $\begingroup$ @Alexander The latter is acceptable. The thing that has to be realistic is the effect the end result would have on your body. $\endgroup$ Oct 4, 2021 at 21:33

7 Answers 7


It shrinks your telomeres

Shortening of telomeres to a critical length triggers a DNA-damage response that contributes to ageing. A new study using a mouse model of accelerated telomere shortening reveals specific transcriptomic and epigenetic changes that provide clues to how telomere shortening is linked to ageing.

I don't know about you, but that statement alone (taken from this source) probably answers it all. Your telomeres are basically a protective "sheath" considered to be there to protect your DNA during cellular division, and probably considered today as the closest thing to an indicator of how much "raw time" we have left as far as I'm aware. Every time your cells divide, they shrink a little bit, always shrinking. Telomere shrinkage is usually associated with aging, and cancer cells, due to intense activity of telomerase (an enzyme that essentially prevents that shrinkage) is the main reason these cells are basically immortal in the sense they won't ever have a limit, unlike normal cells, to how much they can multiply.

Why are they so important? Well I'm not an expert in the field, but as far as my knowledge goes they protect your DNA during cell division, so when they're gone, instead of chipping away at them, the consecutive divisions chip away at your DNA, messing up the cells, creating problems which, theoretically, would essentially culminate in the ideal "death by old age", when your cells are basically too damaged due to sheer passage of time and genetic damage from normal activity to keep working, so you'd essentially drop dead at this point due to wide-scale organ failure.

Basically this spell magically shrinks your telomeres, resulting in exactly zero side effects at first, but resulting in later symptoms of early aging. The more you use it, the shorter you can live without finding a way to regrow your telomeres (meaning that if you do find such a method, you could probably use this spell to your heart's content).

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    $\begingroup$ This is real. Persons with childhood cancer are often cured with radiation and chemo, but the survivors have shorter telomeres and shorter lifespans. news-medical.net/news/20171218/… $\endgroup$
    – Willk
    Oct 4, 2021 at 21:34
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    $\begingroup$ telomeres even shorten the lifespan of clones if stem cells are not harvested. $\endgroup$
    – John
    Oct 4, 2021 at 23:30
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    $\begingroup$ The means for shrinking the telomeres might be something as simple as a really strong dose of thaumic digamma particles --- essentially, magic always leaks a little damaging radiation. Heating up your toast & cheese = negligible to no damage; magically murdering a mob of muggles = death from direct dissociation of your DNA. $\endgroup$
    – elemtilas
    Oct 5, 2021 at 0:14
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    $\begingroup$ Your body generates a chemical called telomerase that naturally lengthens your telomeres over time. In general telomerase will lengthen your telomeres so they keep up with natural cell division; so in a reasonably healthy individual, their telomeres will spring up back to their baseline even if they had been artificially shortened. $\endgroup$
    – Rastilin
    Oct 5, 2021 at 11:51
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    $\begingroup$ @Rastilin Human telomerase isn't available for the entire body, however. Only select bits of your average adult human body. Most cells don't get Telomerase,, and eventually end up unable to divide. This is basically one of the core parts of aging. $\endgroup$
    – Mermaker
    Oct 6, 2021 at 14:31

Introduces a carcinogen to the bloodstream.

A little bit, no prob. We have minor aches and kinks in our system on a daily basis. But the more you use it, the more this builds up in your system, the more it overwhelms your immune system.

And, it comes with a side effect. If you use it a repeatedly but recover? Your immune response might be expecting these sudden 'shocks' to the system and you can potentially develop a host of other problems. Auto-immune diseases, allergies, or a host of other issues.

  • $\begingroup$ "AVADA KED- uchoo!" Takes deep breath. "Where was I?" $\endgroup$ Oct 5, 2021 at 12:15
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    $\begingroup$ Magic-induced chronic diarrhea is a hilarious world feature $\endgroup$
    – Drake P
    Oct 5, 2021 at 18:09

People are still looking for a grand unified theory of aging. There are dozens of aging related reactions that manifest over time as people get older. From telomere shortening as mentioned earlier, to additional factors such as...

  • Senescent Cells, Cells that are damaged enough to no longer be productive and in fact are generating massive waste products but are not dead enough to be recoverable by the immune system. Zombie cells effectively.
  • Mitochondiral damage, proportionately more of the mitochondria have suffered genetic damage to some of their structure, they still generate ATP from glucose, but less efficiently than a healthy set would.
  • Epigenetic damage, the tags that control which genes express where are damaged, so the body isn't producing the right proteins from all of the cells that should be producing any given protein.

Each of these theories is a contender for the biggest cause of aging and all of the theories are being tested in rats as we speak. So you can just take your pick. Go for Epigenetic damage if you want something genuinely permanent, or cell senescence for something that could potentially be more easily reversed.

  • $\begingroup$ Or all three at once! $\endgroup$
    – Mary
    Oct 5, 2021 at 12:10

An accidental Overdose of Gamma Radiation...:

Magic is normally designed to keep the energies involved well contained. Sometimes, however, people want to do things that everyone knows aren't well contained or controlled. They want to cheat safety, but there's a cost. Your "life draining" magics have the same effect of large doses of radiation. Acutely, large doses of this will result in acute radiation poisoning and eventually death. But assumedly the goal is to not die right away.

So your caster will instead aim to suffer the long-term effects. Chronic Radiation poisoning.

Symptoms of chronic radiation syndrome would include, at an early stage, impaired sense of touch and smell and disturbances of the vegetative functions. At a later stage, muscle and skin atrophy and eye cataract follow, with possible fibrous formations on the skin, in case of previous radiation burns. Solid cancer or leukemia due to genetic damage may appear at any time.

So this exposure starts to look a lot like aging. Cancer effects will significantly shorten lifespan as tumors ravage the body.


It creates a homunculus using your actual stem cells

One of the most fundamental (but to outsiders, mysterious) rituals of the wizard concerns the creation of a "little man", a homunculus, within his laboratory glassware. Such a little clone is indeed rather useless in his natural state; yet when bound and transformed by magic to be joined with an object, the homunculus can cast magic repeatedly, just like the wizard he was part of. In this way, homunculi are a visible intermediate in the invisible art of making items that are a permanent source of magical power.

Homunculi are constructed by teleporting a small fraction of the stem cells from the wizard's body, together with other cells to support them, into an arrangement the same as in the wizard ... just smaller. They are heavily assisted by arcane means to regenerate into a tiny wizard body, which has been altered to work on a small scale at least briefly, until it is further transformed.

Unfortunately, removing stem cells has much the same effect on youth as successfully adding them to a person would have ... but in the opposite direction. Every organ has a lowered total regenerative capacity. At first the effect is very small, but the more withdrawals are made, the more severe the limitations of the remaining cells.


completely grounded in realism

The same way any physiological damage to internal organs can cause premature death.

Like: brain concussions, hearth attacks, ruptured spleen, etc. Not so uncommon in martial arts either.


Perhaps I might be barking up the wrong tree but everything your body does requires energy, correct?

Even cells when you get down to the nitty-gritty use chemical energy to perform their basic functions.

So when you're using "life energy" just have it be a uniform drawing on all the energy your body has: potential and kinetic.

If you consider the sum-total of these things as your "life energy" then you can be both realistic and still fulfilling the basic idea.

  • $\begingroup$ But we refill that energy reserve every time we eat. This would not reduce your lifespan any more than strenuous exercise would. $\endgroup$
    – Brianorca
    Oct 6, 2021 at 16:00

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