How can witches be prevented from cannibalizing each other to increase their power?

Question

Mana is the life energy that courses through a metaphysical circulatory system in the human body that allows it to function and perform its daily tasks to keep an individual alive. At the center is the human heart, which pumps mana through all corners of the body in the same way that it pumps blood. The amount of mana content is determined at birth and is different for every individual. Those with a high enough content can access it in a way that allows them to have external effects on the mortal world in the form of spells. This is known as witchcraft, and students of this practice spend years honing their abilities to increase their effects and knowledge to shape the mortal world. These witches range in power, with some born stronger and more talented than others. However, their are ways for individuals to get around this internal handicap to rival others. By consuming the heart of another human, an witch can absorb the mana content lying within the organ. This is done through human sacrifice, in which a witch cuts out the heart of a living victim in an ancient ritual. This adds to their mana capacity and thus their abilities, making them more powerful. Certain witches, known to laypeople as "heartbreakers" take to preying on other humans, killing them and stealing their organs to absorb their mana. Over time, a heartbreakers power accumulates due to compound interest, magnifying their abilities to put them above other rivals.

Heartbreakers are by their very nature evil and sociopathic, and see themselves as superior to their competitors. Sacrificing hundreds of people for their own gain would be standard practice for them. However, the energy they gain from regular people is miniscule, as they possess low levels of mana, forcing them to spend years at playing the long game. It stands to reason that they would hunt other witches in their craft, as their mana content is far higher than that of a normal person. Eating their hearts would provide a significant boost to their own abilities, resulting in a faster accumulation of power with a far lower body count. This accomplishes the goal of increasing their strength much sooner with the added benefit of not drawing attention to themselves by killing hundreds of people. At the very least, they would stack up on consuming regular hearts in order to take on a main rival at some point.

With all the benefits in place, what would prevent evil witches from taking this route?

Answer 1

Mana Prions:

Your witches have particles in themselves that they personally have adapted to handling. While they may harm the witch who has them in some way, the witch manages pretty well to deal with the consequences they've lived with their whole lives. So each witch has some particular weakness that is tied to their mana.

But like prions, eating another witch causes their mana prions to pass into the new witch along with the mana. These magical prions each come with unique problems. Every time you consume another witch, a new set of prions is added to your own.

So a witch who can't eat gluten eats the heart of a witch that is incapable of lying. Now the consumer can't eat gluten OR lie. Eat another witch heart, and suddenly you get violently ill every time you use mana - plus the gluten thing, plus the lying thing.

The stronger the mana, the stronger the prions involved. They may even match the person's personality. A kindly witch is incapable of killing with their power. An evil witch must kill with their power or die. Now the evil witch eats the heart of the kindly witch and is doomed to die because they can't BOTH kill and NOT kill with magic. So you'd need to know your victim's weakness, anticipate its effects on you, and hope it works out.

So while another witch CAN do this kind of thing, the long-term consequences are pretty bad.

Theft

No, not from the witch. A witches coven owns the witches heart. When a witch dies, their hearts are cut out and placed in a canopic jar. What do they do with them? That’s for you to decide. I don’t want to know. Killing a witch makes them angry. But all covens follow a sacred law. Taking a witches heart is like declaring war. There is no rest until the offender is dead and her still-beating heart is claimed as compensation. Your own coven will turn you in.

Answer 2

Missing White Woman Witch Syndrome

In society, there are simply people we care about a lot more than others when they go missing. If a heartbreaker goes around killing a bunch of drifters and junkies, the missing persons will just be added the pile of issues that law enforcement deems not worth the time to heavily pursue, but when a witch goes missing, it's national news worthy. A heartbreaker can get away with killing a lot of nobodies because they can use thier magic to obfuscate thier involvement enough get away with it pretty much every time, but when you kill a witch, everyone in the community will care, especially other witches.

The police will receive countless donations and demands from politically important people to solve the case, they will bring in outside specialists (witch hunters) to aid in identifying and overcoming the charms a heartbreaker may normally us to get away with murder. In short, heartbreaking a witch is a good way to become public enemy #1.

While there is more power in cannibalizing witches, the political backlash means that your odds of getting away with it go WAY down. Sure, you might become a very powerful witch doing this, but that extra power would pale compared to having the collective might of the entire witching community turned against you.

Answer 3

Burn the Witch

Heartbreakers need to kill hundreds of peasants to get much juice. The peasants don't like it. After the first dozen or so, all their cousins form a lynch mob and you get burnt at the stake for being a witch.

Protect our Sisters

Okay, how about the heartbreaker starts as a normal witch, and once she is powerful enough to overcome a peasant mob, she starts heartbreaking? The answer is something I've said before and I'll say it again:

Witches are nice to each other

That's what makes them witches and not sorcerers.

Witches come in covens. The main stat for being a witch is Wisdom and not Intelligence. Witches are highly empathetic creatures. Empathy with the natural world lets them use mana that is not their own. They can manipulate ambient mana and also use their sisters' mana for rituals.

Every competent witch is also empathetic in the normal sense. That means the sociopathic Heartbreakers really stand out in the coven. Most heartbreakers are caught before they leave the coven.

Now suppose -- despite all the obstacles -- an exceptionally talented heartbreaker somehow manages to eat the souls of an entire town. This atrocity leaves a psychic stain on the landscape. The souls of those murdered in agony brush against the nearby leyline. When the local coven does its weekly Commune Ritual they notice something is wrong. They hop on their broomsticks and fly down from the mountain to investigate.

Oath Breakers

The only way a Heartbreaker can be successful is to train herself in secret, without the help of other witches. Then she can start preying on peasants or other witches. But the other witches have safety in numbers, and all share their secrets. So thirteen competent witches easily overpower a single rogue magical prodigy.

The most dangerous Heartbreakers start not as witches but as a type of Warlock. Their initial power comes from making a deal with an otherworldly patron. Then they start heartbreaking until their Witch power is stronger than their Warlock power. Then they use the Witch power to murder their former patron.

Perhaps after murdering their patron they drop the Heartbreaker name and are called Oath Breakers. Or just Warlock. Except I think your world already has those.

Answer 4

A sort of magical Bio-Accumulation

We see this accumulation via consumption in the natural world. For every bit of fish a bigger fish eats, it also gains any pollutants that it's food had within it. A big fish can eat hundreds and thousands of smaller fish over their life span, only to then be eaten by larger sharks, who over time had eaten many large fish. What was but a speck in a tiny fish, is now thousands to millions of specks gathered into a single shark.

This is an actual danger for people who eat a lot of large fish, to make sure only to eat so much of the larger variety (sharks, sail fish, etc) as the amount of bio-accumulation of mercury within them can actually poison you as well as cause pregnant mothers and their babies to have issues.

Something similar may be seen when harvesting hearts to absorb all mana possible. Typcial witches starting down this path will likely attack and sacrifice lower magic beings before they start targeting powerful witches to steal their power. Once a witch has eaten the heart of another, they essentially take in every bit of magical (or biological) pollutants of every being that witch had previously consumed.

Be it "dead-mana" or a bi-product that slowly builds from the use of mana "expended-mana" that never concentrates enough in a single user to cause a problem, but if you were to accumulate 100 times as much as a normal person could ever create themselves, now you've got too much dead/spend-mana weighing you down or causing magical mishaps.

A slow poisoning of mana may also be ignored by those obsessed enough with becoming powerful, accepting the slow decay or whatever negative effects, thinking that the gain in power is worth the tradeoff... any number of ailments could be given at varying levels of Hearts eaten.

A villager heart? No worry. A Witch heart? Take it slower, give a few years between targets to let the bad juju filter out of you to prevent too much dead-mana getting built up.

Mana rejection

Sacrificing a normal person that doesn't use magic is easy, they mind not even know about magic at all.

Once a person starts using mana, their ability to wield this power is a little different between users. Some call forth intent from within, some simply will the magic to perform, while some will use various tools and processes to get do what they need.

This puts a sort of flavor or method of use to the mana. Someone's mana may by more volatile as they channel their emotions to elicit effects that naturally flow from them in times of need, which could overwhelm a more concentrated and focused application of mana that much be pulled out from within rather than channeled as it's already bursting out.

This sort of mana "flavoring" etc may make it too dangerous to eat the heart of another witch without knowing what sort of methods they used to call forth their mana.

A flood of more lethargic, studious mana dumped into a witch that wields mana in a rage, might alter their own mana, or this new mana may essentially be wasted or unintentionally used because the method used by the witch doesn't reach this new variety.

Their heart might even actively reject the mana, seeing it as a poison of sorts and expel it via any means necessary (possibly including explosive results)

Answer 5

Because they will curse themselves if they do.

You can't really start out on your own. A witch who doesn't have a coven and instructors will fumble along and never reach any real power. Consequently, covens have real leverage. And the first spell you must cast is a curse on yourself: that if you ever harm another witch, or attempt to remove this curse, your powers will eat you alive.

That's the only way they feel safe. (And why do they care about witches of other covens? Because a witch-eating witch is dangerous to everyone, way too powerful. Balance of power.)

Answer 6

Because witches' hearts are notoriously disgusting.

It's as simple as that.
Maybe it's the increased metaphysical sinewiness of a heart that needs to pump a lot of mana through its host, or maybe there is something unpalatable about mana itself — whatever the case, eating a raw witch's heart is an infamously distasteful endeavour.

Answer 7

Witches believe themselves a superior species

You state that that these witches feel they are superior, and if you just take that a bit further the problem solves itself. Groups of witches would have their own culture, and this culture could emphasize that it's okay to kill normal people because witches are above humans. To them, killing a powerless human is no crime because they are not people, just prey. Only killing a witch is murder. A witch who kills other witches could become an outcast or be killed.

Answer 8

Risk/Reward

If a witch hunts another witch the odds of them getting killed or severely injured in a magic battle are much higher than if they kill a regular human. Maybe there's a spell that witches can cast if they are about to die that destroys their own heart. It could also release all their magic in an energy blast that destroys everything in the area.

Answer 9

I am Poison

When I realized the power I had, I wanted more.

My first feeding was the day before my twelfth birthday. I lured a friend of my brother into the lake -- you don't need to know how. When he was there, I clasped him in a hug... and then held his head beneath the water until he stopped moving. Cutting out his heart was messy, the first time -- discovering all those ribs, and figuring out to start below them and cut upward -- but the feeling of power was delicious.

I woke up the next day to my mother's singing, greeting me on my twelfth year. I felt joyous, strong. But by the time night fell, I was scared. With my growing power I could defend myself against anyone in town. But what if there were others like me, outside of town? Older, stronger? How could I ever be safe from them?

Sitting by the lake the next day, I was idly fidgeting with an umbrellifer, thinking. My mother had warned me away from this plant -- its sap smelled sweet, but she said that even a bit on the tongue would cause it to swell, choking me. I had always heeded her warning, but in my worry and my growing self-confidence I had sought it out. I smelled my sticky fingers -- like honey. I took a taste -- also like honey. But I could feel the burning start immediately.

I did panic, at first. I remember being embarrassed -- to have gained such power, and to be found choked to death next by my own hand! But I gathered myself, took control, and used my power for the first time on my own body, draining the poison from my tongue, pushing it into my blood.

I was feverish the whole day. The body had been found the day of my birthday -- an accidental drowning, it was assumed -- and my mother thought my illness was fear, a growing girl's recognition of her own mortality. But I was quiet for another reason. I was taking the toxin in my blood and focusing it, feeding it into the muscle of my heart. It made the world dim while I did it, and hurt with a throbbing pain I had never before felt. But over a day or two the pain faded and I grew strong again.

I have fed many times since that first time. Each time I do, I eat the umbrellifer, I concentrate its poison in my heart, and I place another brick in the wall that defends me from those like me. I know the others that feed have the same fears as I do -- but they are powerful like I, and they are smart like I, and they have come to the same answer, or perhaps their own.

For the heart of every witch is a pestilent knot of poison, so concentrated that even a touch would cause death. Only the witch's own living power allows them to survive the poisonous wall they have built; that, and the resistance that comes with time and exposure. To eat a witch safely, one would have to find a very young witch, a very dumb witch... or that one witch in a thousand who chose the same poison as you. But what witch would share the mortal secret of what their poison is?