# How could reincarnation magic be limited to prevent overuse?

Maleficient is an evil witch on a quest for true immortality. Until she accomplishes her goal, she uses a midpoint form of magic called reincarnation in order to buy her more time and keep her alive. Reincarnation magic allows an individual to reincarnate themselves after death in the body of another human. Maleficient has a number of host bodies scattered throughout the world and trapped in a deep sleep to take control of in case she is killed by her enemies or dies of old age. Her most recent claim, a young girl named Snow White, is the next host that she will possess.

This spell takes a number of steps. After a person dies, their soul jumps into a magical item called a soul stone, which keeps the soul in storage and prevents it from crossing over to the next world. The soul is then transported and absorbed into the host body, giving the person possession over it. Reincarnation requires the victim to be living, so these hosts are placed in a coma-like sleep and kept in magical stasis to prevent them from aging. They are stored in this way until needed for further use.

The result is that the body now contains two souls within it that continue to remain separate, with the original soul remaining trapped and the dominant soul of the witch retaining control. The witch now has access to the person's memories, knowledge and spells to use. They can also access the person's mana for an extra boost in spellcasting if needed.

Powerful witches are likely to use this method to cheat death whenever possible, and limits need to be places on this form of magic to prevent constant overuse. In essence, individuals both weak and strong should only reincarnate themselves into others of their caliber. A witch might be powerful, but would have a hard time with this spell because there are few people walking around with that kind of power level. Alternatively, an average person would have an easier time because of a larger pool of individuals. However, this isn't a power grab. Even if they managed to take down a powerful opponent, transporting their own soul into them wouldn't be an option.

How can I accomplish this goal with these rules?

• Why do you call it reincarnation rather than possession? – Artur Biesiadowski Sep 2 '19 at 8:26
• I basically reads like a quote from a pen and paper fantasy game rule book I have played.... @ArturBiesiadowski If true (or maybe even if not), this could become a question on rpg.stackexchange.com – Yunnosch Sep 3 '19 at 6:30

The magic ability depends on the body capabilities

Just as are able to lift more weight by training, magic strength also needs to be cultivated. As such, after moving to a new body, the witch may have the knowledge of very advanced spells, but would actually be unable to perform them, as their new body will be unable to channel such level of magic.

The witch will need to train within her new body in order to slowly gain up a decent ability at witchcraft. While her previous experience will help somewhat, and we should assume that she will have chosen a body with some innate ability at magic, it will have no magic at all, so the host abilities will be completely atrophied, and getting up to high magic levels will take many years (a normal apprentice will slowly grow uup his magic capabilities in their normal learning, but here it's like having the brain of a scientific inside the body of a baby).

(By the way, after being in magical comma for years, the host will also be physically atrophied, although that's easier to overcome)

Note that regarding your third paragraph, I don't think the witch should have access to both that person's memories, knowledge, spells and mana and her own ones. If the memories are stored in the body, the witch would lose her own memories when moving to a new one. If they are instead linked to the soul, she would keep them, but would have no access to the host ones.

In order to have it somewhat balanced and interesting, I would recommend letting the witch keep her memories (memories from Snow White before she was trapped -10 years ago- wouldn't be too useful anyway) but have the available mana restricted by the host body.

• This is sort of the answer I was going to write: the reincarnation spell costs mana and mana is inherent to the body (not the soul). So if you want to cast a 100-mana spell when possessing a 10-mana body, you will have to train hard before you can do so. – Bernat Sep 2 '19 at 19:56
• The spell needed to keep a body comatose and yet healthy for a long period of time HAS to be very powerful, we can't even accomplish that with modern technology. so there also has to be a limit to how many such spells a witch can keep going at the same time. Worse it is unlikely they could maintain such spells during the transfer so it is unlikely you could have more than one back up at a time. – John Jan 13 '20 at 0:15

Remember analogue audio tapes? Copying them was a lossy process: If copied too often, you'd accumulate noise until the content is no longer enjoyable.

Make soul transfer a lossy process, too. Applied once, there's almost no change in the soul, but with each transfer, damage to the soul accumulates, until at some point it is too weak to take over the new body. It is still there, but the actual owner of the body is now in control, and can in turn make use of the witch's memories and powers.

• Memory loss will do just fine. If you have 1% chance of not knowing your ---laptop password--- demon servant's true name or ---username--- the location of your lair each time you jump to a different body, you will think twice before doing that too often. – John Dvorak Sep 1 '19 at 8:45
• JPEG artifacts are not something you want on your soul. – IndigoFenix Sep 1 '19 at 12:02
• There could even be some bleed over of each host's personality, so that Maleficient has to go out and find an initially weak-willed host whose personality she can dominate, or otherwise a sufficiently like-minded person so that the bleed-over will be manageable. Maybe some people only accept their closest friends as hosts. – user7868 Sep 2 '19 at 8:08
• I actually recall a Doctor Who audio story Immortal Beloved, which touched on this kind of idea. There were characters who would copy their minds into younger clones of themselves to achieve immortality but there was the implication that repeating this process over and over caused degradation in both their memory and personality over time. Rather than making them weaker, though, the risk was more that they'd lose their sense of self and that they would perhaps become more deranged. – DoctorPenguin Sep 2 '19 at 10:20
• It was also the premise behind the Asgard in Stargate and TNG's Up the Long Ladder episode. – Jontia May 7 '20 at 11:28
1. Don't make the base witch inherently dominant. It should be a tough struggle of wills to take control of the new host. Of course, a skilled witch will be very skilled at soul combat, and have spells to pacify the other soul, but make it a struggle. The base soul is more suited for their body, so if they are trained in soul defense they may be the one who controls the body.

2. Make the souls an attractive target for any witch who wants power. The soul of a powerful witch, free of her body, could be a powerful ingredient in many spells, warding schemes, and potions that other witches could want. If you do die and anyone finds out, many witches will attempt to ambush and steal your soul. There's a strong incentive for whoever is managing the soul to sell it to any of many willing buyers.

3. Make soul transportation difficult. Losing your body and mastering the soul of another should be exhausting. During this time the witch is vulnerable to others stealing her secrets with mind magic, or being attacked.

• Also, with regard to point (3), even after finally getting control of the body, the witch may be exhausted and require time to recover, during which she is more vulnerable. – Matthieu M. Sep 2 '19 at 13:09

## Loss of spell

What powers the spell is the spell itself: It unravels all memory of itself and how to get that knowledge, and uses that energy as a kickstarter. A clever witch will have given herself clues, left parts of it scattered around where only she can find or understand it, but finding the spell again will take time. Writing it down where everyone can find it, will be too dangerous, since she is not able to defend herself once in the stone, so it must be hidden cleverly. Most people only manage it once. They die, having spent their priceless, second life frantically searching without success.

I can think of a few ways. First, soul stones could be hard to make and degrade with each transfer to a new host body. The chances of it failing to retain the soul during the transfer go up each time it’s done. Thus, the witch risks crossing over to the afterlife more. And making a new soul stone can’t be done without potentially breaking the artificial attachment to the new host body.

Second, with each transfer, the pool of compatible hosts decreases. You absorb traits from each host body, which means the list of traits you have to match gets longer. That increases the difficulty finding potential hosts.

Third, potential insanity. Your soul might have an allergic reaction to the host body, causing you to gradually lose your mind.

## Biological compatibility

As with organ transplants, the soul must be transplanted to a compatible body, in sufficiently good health that the shock won't kill them; else the transplantation process will fail. I would suspect that there wouldn't be too many people meeting the criteria, which is generally the case when looking for donors.

Secondly, the soulstone is a physical item, which needs time to be formed within the original body of the witch or within the host's body, so the witch can't just body hop whenever. Add on that the soulstone is a one shot: once the witch dies, the soulstone has to be physically transferred to the new host, where it will break down and transfer the soul into the host's body. Afterwards, the witch will have to generate a new soulstone for the next transfer, which would take a couple of years to do.

I think that having the host bodies retain a portion or remnants of its previous 'soul', that fuses with your own when you resurrect in said body is an interesting option.

When you resurrect, this fragments are fused with your own soul, maybe giving it a good side like random useful memories or skills, but mostly making you... less like you were, maybe haunted by thoughts that are not your own, resentment, and ill feelings toward yourself for 'stealing' that body

Resurrection Sickness.

Once the Host Body has been taken over, the Supplanter needs time to 'settle in'. During this period, their Magical prowess is severely stunted (for the first few days, they can't cast any spells!), gradually regaining their abilities as the body adapts to their soul. As the Host Body cannot have many protective enchantments in place beforehand - both to avoid disrupting the Stasis Seal, and also so that you don't accidentally protect them from Possession - it will take time before the Witch is warded and prepared to reveal their survival.

Even worse, they are unable to create a new Soul Stone during this period - so if they are killed again, they're dead for good!

This is a "life-boat", or "emergency bug-out" spell - not something to use every time a tasty looking new body comes along.

Powerful spellcasters tend to prepare traps that will destroy their body (explosively, or with other AoE effects) once their soul is no longer in residence - not only does this prevent their killers from locating the Soul Stone, it also makes them a very bad choice of Host for their rivals. Instead, they find naïve youngsters with prestigious natural talent, nurture them in a way which prevents them from becoming a genuine threat (or protecting themselves) and then put them into Stasis once they're "ripe".

This also gives them a strategy for when "old age" is catching up with them: ingratiate themselves as a kindly crone to a nearby monarch with a young and magically talented daughter. Teach the daughter 'useless' magic such as "empathy" or "animal communication" to boost her reserves, and beauty magic to sculpt her form. Then, reveal your evilness in an over-the-top manner, kidnap the princess to a nearby evil castle, copy her memories, and wait for a hero to be called. The hero slays the Witch, and starts working through traps to rescue the princess. Meanwhile, a loyal minion (patiently waiting outside the blast radius) grabs the Soul Stone, hightails it through a secret passage, performs the possession ritual, and then feeds the Witch an "enchanted sleep" potion. The hero then rescues the "princess", who seems shaken and slightly changed by her harrowing ordeal, while no sign of the Witch can be found...

• The "resurrection sickness" part reminds me of the post-regeneration episodes of Doctor Who. – The Daleks Jan 13 '20 at 0:05

Witch can't take over a more powerful witch because the more powerful witch wins, and the invading soul is killed and/or absorbed. Thus the more powerful witch absorbs the inferior witch so the witch has to select an equal or lesser body.

If a witch takes a lower body it diminishes her own magic levels.

You then scale these by percentage to weakly or strongly enforce these rules.

Therefore a witch selects a someone within say 1% of there abilities.

You can introduce witch hunters to hunt witches as they have methods to detect witches in her dormant state or you could also make soul becomes weaker every time reincarnation magic used till it threatened to disappear. You can also introduce supernatural forces like Grim reapers to kill witches if they cheat death too much.

The spell itself is powered by another witch, not the one being reincarnated. (After all, the one to be reincarnated is trapped in the crystal.) This makes the reincarnation candidate vulnerable.

1. If I'm the #2 witch after the now-deceased #1, there are a couple of factors that would influence me. First, a powerful soul trapped in a crystal might be useful for creating powerful magical items. (For me, of course.) Second, if I'm #2 but I can become #1 by an unfortunate and unforseen accident happening during the reincarnation, where exactly is my motivation to succeed? I would of course selflessly take up the burden of continuing the master's studies...

2. The one performing the ceremony might honestly fail. They are the apprentice (or competitor), after all.

A second line of options would revolve around the actual takeover of the host.

1. The host's soul may in fact overpower the reincarnated one -- it is their body after all and you can have a strong inner will without being magically powerful. So the reincarnation candidate has to deal with the distinct possibility that they will will be the victim rather than the victor. A lifetime of magical training, handed over to some peasant who happened to be strong on the inside. (This raises the additional plot point that it may not be easy to tell if the ceremony worked one way or the other. The victorious host would have access to the witch's memories, remember.)

2. The witch doesn't subdue the host once for all time. Rather, they must dominate and work through the host. If the struggle is too severe, the host could be mentally damaged so badly that the witch is trapped within a barely-functional host. Sort of like a sharp mind trapped in a disease-ravaged body. Not to mention that the constant fighting and need to domineer makes the reincarnation less desirable than it might otherwise be. Only the supremely (over) confident would attempt it.

(And this is a key point: if you do the ceremony, it works, you take over the body with no risk or pain and the previous owner is at your beck and call, it's hard to see how it wouldn't be enormously popular. There has to be a downside for the witch and I like the idea that they continue to exist and gain power, but it's not a pleasant existence.)

Your hypothetical witch can do it whenever she wants, and with guaranteed success, but it causes psychological problems. You see, as part of the transfer process, the host's brain is completely wiped. While this removes any possibility of the host revolting, it also wipes the ambulatory parts of the brain. This has the side effect that, when your hypothetical witch first takes over the body, she can't move or take care of herself; somebody else has to do these things for her. This is a major shock to her mind, causing instability. To compound this, every time the witch looks in the mirror she will see someone else's face; a face which she last saw in incredible pain. The combined shocks would really mess with the witch's mind, often making her become a schizophrenic. For further reading on this subject, I suggest that you read Robert A. Heinlein's book I Will Fear No Evil. It pretty much covers your question.

Why invent anything different that plain old high mana/ingridients cost? The spell is so complex, that it requires a lot of magical energy stored up. Collecting it in such amount is difficult and takes years by performing (insert a list of non-trivial time and effort consuming tasks). Unless witch fails to complete this preparation in time for next cast it is game over for her. And if there are people working on killing her, "in time" might come quite quick and unexpected.

I doubt that anything that is not "Worse than death" would make such a character think twice before doing it. In fact such a character would probably have a combination of ego and determination that would over-ride any potential side effects. I think you would have to make it circumstantial. In such a sway, that an ingredient to perform the spell is so rare and difficult to attain that only one is ever in existence at any time, and your villain has access to the thing that makes it. That creates a very finite cap to who and how many.

Resurrection and Reincarnation magic is a big, probably the most powerful, type of magic. It allows for the worst consequence normally associated with life... Death... to be diminished as a result. I'm, kind of, of the opinion that when a bad guy who uses such magic finally is "hoisted by their own petard" their ultimate death should be as awful as dying as many times as they effectively lived. The circumstances of which should make for a fun brainstorming session for any writer/DM.

If, however, you want the spell to be accessible to everyone, but on a limited basis, it's not a problem to just apply an arbitrary number.

Example in modern fiction: Doctor Who is one of the most popular sci fi shows ever made. When the Doctor "dies" he regenerates into a new form. (Or in certain situations uses the regeneration power to heal himself in the same form)

Time Lords are limited to 13 incarnations (12 regenerations) under normal circumstances, and within the bounds of the show only two of the most powerful; The Master (Three times) and The Doctor, ever overcame this issue.

The Master stole the power of The Keeper of Traken and used it to steal the body of a man called Tremas, (note the anagram...) to beat the limit, then survived a Dalek execution before possessing Eric Roberts and was subsequently "resurrected" by The Timelords after he died facing off against the 8th Doctor. He was willing to go to any length to continue his existence. While the Doctor was granted a new set of regenerations despite being ready to accept his fate, essentially so that he could keep up his good work...

Yet no one has ever asked the question, "So... why do they only get 12 regenerations and not 120???" and they don't need to. That part of the story is unimportant next to what that limit means to the various characters.

Reincarnation spell does need an enormous amount of mana, which is waaaay over any human capabilities to generate "at once", even for a powerful witch as Maleficient.

The spell involves two aspects:

1. raw mana needed to perform the transfer and sustain the witch's soul during the process and the time it is trapped in the soulstone;

2. protect the soul from "Beings of Incommensurate Terror, Cosmic Hallucinations and Eaters of Souls", let's call them big baddies for short!

Big baddies feed on evil souls. Should Maleficient die and try to reincarnate without proper protection, they will sense that an evil soul with enormous power is lingering around instead of passing to the next world. Big baddies will crave that evil powered soul and, if given the possibility, they will eat it. Sorry, dear Maleficient, no arguing with big baddies!

To prevent this, the soul must be concealed by a magical "shield" that must retain its effectiveness during the whole process, from the death of the witch until her soul completes the possession of the new body. The shield is like a supernatural cloaking device. It makes the big baddies completely unaware of the witch's soul.

The mana for the reincarnation spell must be available instantly upon death, so it must be preemptively stored in the soulstone, which acts also as a mana tank for the spell and its cloaking shield.

All the mana required to fuel the shield must be collected and stored by the witch during a looong period of time because (a) the quantity is very big, (b) she needs mana for her everyday evil acts, so she can't spend too much mana on building up the mana reserve in the soulstone. Moreover she could not let her minions funnel mana into the soulstone by other means. The mana must come from the witch herself, because it must be "tuned" to her very soul.

So the process of preparing the soulstone and filling it up with mana is tedious and requires daily effort by the witch. If she wants to fill it more quickly, she must avoid using mana for everyday magic. So, dear Maleficient, do you want a quicker refill today? Then no transforming farmers into pigs nor mesmerizing young princes till tomorrow, sorry!

The more mana stored in the soulstone, the longer the soul can safely be stored in it. So the witch must plan carefully how much her soulstone must be filled with mana to give her a reasonable amount of time to complete the process.

Moreover, dear Maleficient, the process takes more and more time as you fill-up the soulstone, because it becomes more dangerous if done incorrectly or hastily. You wouldn't want to overload a soulstone filled with $$10 MGf$$ of mana, would you?!?

BTW $$Gf$$ stands for Gandalf, the SI unit for measuring mana, so that's 10 megaGandalf. And, yes, we build worlds, so we measure things using SI, not that imperial rubbish (we abolished the old Merlin unit loooong ago!).

And since there is no escape from the big baddies except for passing to the next world... you better put enough bee... (*cough*) ... mana in your ke...(*cough*)... soulstone.

So, dear Maleficient, your calculations show that you need $$1.21 GGf$$ of mana? You better store 4 because, you know, dumb minions, unwelcome heroes, unexpected divine intervention, sloppy soulstone schematics, and ... Murphy!

Here's my few ways of limiting the process.

1. Soulstones are unique.

The soulstone you make on your original body is the only one you will ever be able to use. If you try to make one while posessing someone else, you will be making a soulstone for their soul, not yours. If you make multiple soulstones on your original body, you'll be stuck bouncing between them until there's only one left, as aside from the transfer process, the stones take priority for where your soul goes.

Transferring a soul out of a soulstone degrades the stone. Eventually you'll have a resurrection where the stone shatters during transfer. Coupled with uniqueness, this means that if you wake up after resurrection and find your soulstone shattered, you know you won't be getting another one.

3. Multiple spells on an object can interfere with each other.

This prevents you from just using a repair spell on a degraded soulstone. It'll interfere with the soulstone magic and stop it from working as one, which with the uniqueness problem, would render you unable to get another resurrection as surely as if the stone had shattered. Won't stop non-magical repair with clarketech, though that might be far-enough off into the future that it won't matter for your story.

4. Materials to make a soulstone are rare.

If the stone itself is manufactured, as opposed to using magic on an existing gemstone (which is probably rare, anyway), then the materials needed to manufacture the base stone might just be rare and expensive, so not that many people end up making them simply due to lack of funds.

That's just sticking to the soulstone itself. Posessing another person could bring its own set of challenges, as could potential sabotage from rivals.

# It's a trap!

Battling another witch, magic vs magic, is a highly risky prospect for either side.

Sneakily locating a witch's sleeping host and poisoning/trapping the body to imprison her, however, is much less risky. And there's a variety here: the soul of the witch may simply be disposed of, or it may be trapped and tapped for power or secrets. There's even rumors the particularly evil witches managed to make slaves of others by implementing conditioned triggers in their rivals using this method.

This means that a witch must be very careful to remain undetected when preparing a host, must regularly check the integrity of her hosts without divulging their locations, and there is still, at the end, a risk of being outright killed or entrapped when attempting to take possession of the host body.

This means that:

• Dying is costly: a new host has to be prepared, presumably in a new location if the soul's travel can be tracked.
• Dying is risky.

And thus, despite being able to trump death, witches may be leery to overuse their safety net.

## Increasing Pain

Any possession gives low-key pain constantly while possessing it. This increases with every subsequent jump, so people with this form of immortality pay a hefty price if forced to switch, and therefore will attempt to find a better method of immortality.

This helps you keep this as "midpoint immortality". Of course, strong-willed individuals can keep doing this for X jumps without real adverse effects, but it stops somewhere for everyone.

## If you possess someone stronger...

Then the victim might take over from you, and you risk your continued existence by this method. Therefore, this is a stupid thing to do. You might be able to keep it up for a while, but not for long.

They are, after all, stronger than you.

## If you possess someone weaker...

Then your new power becomes the average of your own and that of the body, perhaps slightly higher to enable you to gain power by possessing someone close enough like you mentioned.

Kind of sounds like Orochimaru's jutsu from Naruto. In this series, the overtaking of the new host body had a 2 year timer before it could be performed again. No explanation given, just convenient to the plot.

The "soul stone" logistics also seem a bit difficult to handle in real life. Taking it from a corpse in the battlefield and then transporting it to the new host? It requires a very loyal servant (or someone really invested in the witch's resurrection) to do it. Plus, if the witch was killed in battle, what are the odds that her enemy would not simply destroy/hide this soul stone?

What defines this power level matching? Is it physical? Will power? Magic wisdom? What if the hero gives the soul to a frog host (Goku-Gyniu style). Backlashes such as these add risk to using such spell.

What if the soul stone is never taken to the new host? Does the trapped soul becomes imprisoned without being able to move on to the afterlife? Seems pretty scary on its own. As a bonus, you could claim this period in the soul stone to be a hell-like experience, an immensely painful experience that would drive any living being to suicide. This would mean that only a being of incredible will-power and ambition would attempt this trick more than once.

The first thing that comes to mind is that playing with the soul can attract the attention of powerful entities -- Gods, Demons, Truth -- and they will certainly have reactions to what the witch is trying. They are messing with the Celestial Bureaucracy and that could have Consequences. Meddling with the Soul is going to cost you, and potentially more than just an arm and a sibling. This danger alone might deter the less ambitious.

But reading it through, the whole process itself is laden with pratfalls and traps that have to be navigated through for a successful reincarnation. The trick is to look at what you have and go "Where can this go wrong, O Great Murphy?"

The other big question is how common is this spell? If this ritual is widely disseminated, then the pratfalls are likely known and you will likely see more care taken. Otherwise, experience may be the teacher, the cruel grinning teacher.

## Hapless Victim

Compatibility

Her most recent claim, a young girl named Snow White, is the next host that she will possess.

First, there is the victim. The witch requires not only a physically able and compatible body to take over (mentioned already), but a magically compatible one as well. Has Ms. White been checked over to ensure this level of compatibility?

The premise behind this is that a good number of shows, games, and stories portray magic has having some manner of alignment between people, and it is those alignments that need to be taken into account when transferring to that body. It is certainly possibly to groom an aspiring body to have something acceptably close to your alignment, but depending on the witch's alignment (and spell preferences), this might be a tricky endeavour. Snow White cursing the animals while she sings along with them might be noticed.

This magical compatibility can extend to other magical parameters as well. However other parameters are easy enough to groom for with enough effort and/or time so those tend to be secondary for all but the most immediate emergency reincarnations.

Note to aspiring ritualists: Find the sane ones to take over. Distorted mages are dangerous -- even barely trained ones. No matter how tempting the target, Do Not Engage.

Preparation

Next, I would assume that the victim would need to be prepared in some way. Perhaps this does not need to be an elaborate or expensive preparation, but it is an extra step. While not vital to the process, this step allows the whole process to run smoother and permit a higher chance of success (or lower chance of side effects) than not doing it. Jealous witches may guard this secret step knowing that this is their secret to success, limiting its propagation out into the general magic knowledge.

The limitation here can be that once a body is prepared for the transference ritual, the process has started and a different body can't be chosen until the process is complete or aborted. The pause between this step and the next one can be indefinite, but it needs to continue.

## The Ritual

After a person dies, their soul jumps into a magical item called a soul stone, which keeps the soul in storage and prevents it from crossing over to the next world.

The Stone for the Soul

First, the stone. The obvious limitation is that the soul stone needs to be of impeccable quality. The more flawless the stone, the more flawless the soul storage is. Here is where the lossy storage starts to really happen -- only a perfect gem can house a soul without consequence, and if the gem is rendered unusable for a second ritual then sourcing the gem is a definite limiting factor. The more one looks for that flawless gem, the more questions might be raised.

The witch's vanity may also be a limiting factor. Either through bad information, deliberate sabotage by another witch, or simply their own vanity, they have decided that a diamond is their soul stone. It may very well be that an amethyst, quartz, or other lower value and/or more common gem would not only be easier to source for the needed quality, but actually be more compatible with the witch. This leads to the first point regarding quality of the storage medium.

A third limit might be the preparation of the stone itself. Arcane rituals might need to simmer for weeks, months, or even years before the stone is properly ready to house a soul. Said rituals might not need a lot of personal time, but they do still need to happen.

The Soul in the Stone

The first obvious limit is that the caster needs to die. But what is the stone's effective range? If a witch's soul stone is safely ensconced in their laboratory and they are killed kilometers away trying to deal with the pesky interlopers, will the stone still trap her soul?

The next question is how dead is dead? While the question might seem redundant, is a vegetative +coma enough to trigger the transfer? Is being mostly dead but not quite dead enough dead to be considered dead? I could see the same enchanted coma that works to preserve the victims actually preventing the ritual from happening if used on the witch.

Third, how close does the stone need to be to transfer into the new host and how long does one have to do the actual transfer of souls?

## The Results

The soul is then transported and absorbed into the host body, giving the person possession over it

The result is that the body now contains two souls within it that continue to remain separate, with the original soul remaining trapped and the dominant soul of the witch retaining control.

Possession is Nine-Tenths of the Spell

The Possession part is the biggest pratfall -- You are an invader and your prospective host wants you out. The combat might be brief, it might be protracted, but it happens and is the heart of the ritual. This is the crucial winner-take-all part of the spell and why you are here. The witch has the advantage in preparation but the victim has home-field advantage. The winner gets the body and the loser gets locked away until the chance to strike again occurs. Obviously the witch will metaphorically stack the deck in her favour for this part, but natural talent in this area can't be underestimated.

This might not even be a conscious act by the victim -- See the immune system for why we don't just allow any old foreign thing into our bodies.

The Perils of Winning

So now you have a new (hopefully) younger body, and another lifetime to plan. Well there was one little problem that you only realized as you started exploding. You, the soul of the witch, might be able to channel vast amounts of arcane awesomeness but the young person you just bodyjacked can't. You who are so used to channeling so much power will literally overload your new body's capacity and cause a catastrophic physical failure due to this.

To put it simply, your mind and soul might know how to channel a metric Gandalf-ton of power, but the body you are not in certainly can't handle it and has never been trained to do it since that training would make your victim a threat.

Likewise the opposite might hold -- you can't channel that much, and now the body your in draws in and handles several times what you are capable of wielding safely. All the magic that the body has to go somewhere but you can't actually handle the task of using it. This is almost certainly going to ... interesting.

Other magical side effects are likely possible leading to a trope of the newly reincarnated sequestering themselves in their layer for a time to acclimatize themselves to their new body. Ultimately this is derived from finding a magically compatible host, mentioned above.

## Rereincarnation

So you want to reincarnate again ... great! One problem ... two souls in one body. While in theory, one soul is dominant while the other submissive, but how true is that really? Can a second soul gem only grab the witch's soul? Again, this is where your equal strength qualifier comes in -- Souls holding equal power are actually better able to hold their individuality. This might seem counterintuitive at first glance but consider that if one is vastly more powerful than the other, the powerful ego will either crush the lesser one leaving soul rubble to clean up and maybe attract bad attention, or draw the lesser ego/soul into itself thus muddying the original soul and causing complications further down the line.

## Conclusion

The victim and the gem itself appear to be your two biggest pinch points for a successful reincarnation. Unless everything has to be absolutely perfect for the spell to work at all, then I would think that it becomes a case of weighing the options and trying it when they are ready.

Also don't worry if they didn't do a perfect job, failure is always an option. In this case, it can lead to interesting consequences if that is a direction you want to go.

Final Note: It would be ill advised to kidnap Ms. White for this kind of thing as her great-grandmother Betty is older, wiser, better with animals and has spent years being old and powerful without reincarnating.

Multiple Personality Disorder

If the witch may be able to successfully transfer into the host, their soul may not be able to take control of the host's body indefinitely, and for some certain moments of time the host's soul may become the dominant one, the one actively controlling the body. This leads to a power struggle outwardly manifested as multiple personality disorder, where both souls alternate control of the body for periods of time. The swapping points may be triggered by a full moon, or just by psychological events like feeling certain emotions or having great mental stress, such as attempting to cast a spell. In that case, the witch's soul loses power and the host's soul takes over.

When you bind your soul to a host a bit of the binding remains stuck in the host forever, the next time you bind it will be a bit harder. You must continue to improve your power or eventually you will reach the point that your power isn't enough to bind your soul to the new host.