There might be a really obvious reason this wouldn't work that I'm not thinking of, but... okay, so Creo spells need vis-expending Rituals to instantly create permanent stuff, but they don't need vis or Ritual to improve/accelerate a living thing's existing capacity for creation. Creo can make animals grow to maturity faster or give people a bonus to Recovery rolls, because bodies naturally try to heal and grow, but instantly healing wounds takes a Ritual and thus vis. Muto spells, meanwhile, can change something's essential nature, but only for as long as the magical effect is maintained.
So if you had someone missing, say, an arm or an eye, could you use a Corpus effect implementing both Muto and Creo as requisites to give someone the ability to heal parts of their body people normally can't, and maintain that effect until the body healed itself to heal those injuries without expending vis?
There is no MuCo guideline to transform a human sufficiently to give it strong supernatural abilities like improved self-healing. There is a MuAn guideline (ArM5 p.118 box):
Give an animal a "magical" ability such as the ability to breathe fire (requires a requisite for the ability).
So a Bjornaer in Heartbeast form may benefit from a MuAn spell bestowing an ability to slowly regrow a leg or an eye. But the magnitude of the spell would make it a ritual needing vis expenditure. Many Bjornaer would also try to resist it.
Making a similar MuCo ritual requires a new guideline - likely as a Breakthrough. Once Marcus Tauros of Criamon (MoH p.79ff, especially p.83 box New Virtue: Hermetic Metamorphosis) has completed his research, he might perhaps help.
If it is a serious goal of a character, the player should discuss it with their troupe.
There may be another approach a maga with a deep knowledge of nature may attempt:
Turn a human into an animal with natural regeneration like a salamander, then have it renerate the specific wound, finally turn it back to human.
Such MuCo(An) spells, especially if maintained over time, can however (by ArM5 p.132 box) have lasting aftereffects.
This is a really cool and innovative idea about hermetic healing! I really appreciate you sharing it with the forum, since it's created some interesting discussion with my playgroup.
I think the answer to this question depends a bit on the context surrounding it. In play, it can be better to be permissive for the sake of a good story or cool player idea for resolving a problem.
If the question is purely about if this lies within Hermetic Theory, then I think the other posts in this thread offer some really good points. In my game, we ruled that there is a Corpus guideline that's equivalent to the Animal guideline that grants supernatural powers- because of that, this would work in my game so long as the magic is sustained long enough for the injury to heal (I would assume it heals as a Heavy Wound). If this takes long enough, it could easily lead to warping.
Your saga could rule likewise, or decide that another hermetic wizard completed such a project as a Breakthrough. This is especially appropriate if it was a spur-of-the-moment sort of a idea, or one that you don't feel the story is going to linger on very much (or one you aren't interested in getting a lot of spotlight- sometimes you just want to move the story forward.)
If you were interested in telling a story of research that takes a lot of time, this could be a good candidate for a Minor Breakthrough- presumably one that draws on the Animal guideline.
@OneShot I'm not so sure! After all, the very lowest-level example MuCo spell uses an Animal requisite to give someone the eyes of a cat, which enhances their sight to being able to see in the dark. It seems like decidedly unnatural improvements can be achieved with the right requisite as long as they're relatively small expansions on existing abilities - people can see, so MuCo(An) can make them see in situations they normally couldn't. Conversely, since Corpus is associated with healing, and people do naturally have the ability to heal from injuries, it makes it seem plausible to me that "healing from injuries they normally couldn't" is within the bounds of Mu(Cr)Co. Idk though, that's just where I'm at at the moment, it might not hold up.
@Zaleramancer Aw, thank you for the kind words! I'm glad I could help spark fun talk in your group. As far as context, the situation that inspired this line of questioning is pretty atypical - I'm actually solo-running and writing a side story based on an antagonist from a prior campaign being forced into a quest to atone for her actions, and after being brutally wounded in a battle, she sent off her one uninjured companion with her accumulated vis to bargain for help from a nearby covenant as a last-ditch effort to ensure her and her new companions wouldn't die from their injuries. It worked and the group survived, but one party member lost an eye and she herself had to get her arm amputated. I ultimately decided it was better for the story if she had to live with those consequences, but it still sparked the thought experiment over whether the magus doing the healing would have any options to help that weren't more expensive than the amount of vis they had on hand to offer for service.
This is more or less what I told you above. Body of the Newt should give the person to be healed the capability for regeneration you wish them to have - provided your maga character gets the idea.
Healing just eyes or arms via potentially lower level guideline Leg of the Newt or Eye of the Newt looks a little bit more fishy, and might also require invention of multiple spells. But that is decided by your SG or troupe - and if you solo it, by you.
Suppose that Body of the Newt indeed allows for regeneration of stuff that would not otherwise regenerate. It's not obvious it would still do so if cast on a person already not whole. I.e. it might be that if you first cast the spell on a man, then blind him, he heals but if you first blind him, and then cast the spell, he won't heal. The spell would bring him back to his initial state, but that is the state at time the spell is cast.
Now, with this limitation (spell must be active before damage occurs), and some extra magnitudes compared to the Base 2 MuCo guideline (because limb-and-eye regeneration is clearly not a minor ability), I would allow regeneration to occur -- roughly at the rate at which the effects of disabling Perdo spells are healed.
It is an idea hinted at in several places. TME mentions it in the "Unnatural Stones" section on p.58 when covering possible changes to the outer stone wall of a floating island.
"A wall that heals itself requires a Requisite of one of the living Arts: Animal, Corpus or Herbam. Of these, Herbam is the least disgusting: plants do not bleed and scab while healing."
Pretty sure you cannot recreate an missing eye or arm with a Muto spell, as Muto says you are altering something from one form to another. But the arm or eye are missing....... So this definitely is a Creo Spell.
But what probably would work IMO is to alter the rate of natural healing of the body as long as the spell is working. If the spell speeds up natural healing processes you may recover from a heavy wound in maybe one day e.g. And in this case no VIS would be required.
But a missing body part ist simply a missing body part and you will need Creo for recreating and Vis for making it permanent.
I mean, Muto magic can produce effects that do result in changes to the overall form of something.
If you transform a rock into water, it will pool and then, when the spell ends* it will likely remain in the new shape it was in. There's a canonical spell in the HoH:S book for transforming a object into species that changes the final shape of the object after the magic ends.
*depending on the way the wizard designed the spell.
I would encourage there to be a Creo Requisite for such a spell, but Muto magic can change the properties of things in ways that can result in permanent indirect changes to the affected substance.
Not sure but one could say it is possibly a Rego Corporem or a Muto Corporem spell if you want to speed up natural healing. But I don't really see why a Creo requisite should be added?
Speeding up natural healing is just Creo Corpus. The hypothetical Muto Corpus (Creo requisite) effect is to expand the scope of what kind of healing your body can naturally do. Just like a Muto Corpus (Animal) effect can turn you into a bird, and then you can fly somewhere high that you couldn't reach otherwise, and then the spell ends and you turn back into a person, and you'll still be up there even though you can no longer fly; can you make yourself capable of regrowing eyes or limbs, keep the spell going for however long that takes, and then when the spell ends the thing you regrew is still regrown, even though the ability to regrow it no longer persists? (Okay, Zaleramancer's example of turning a rock into water and back and its shape changing is actually better than the bird one, but I didn't wanna copycat.) That's the question I made the thread to answer. Gotten a lot of interesting answers so far.
If a self-repairing wall is possible, it lends credence to the idea that making a person self-repairing is also possible.
I think so too.... The obstacles in the rules for healing magic are there because the authors intended to have a dangerous wound system with long time to heal.... but not because of internal logic of the magic system.
If you compare with other Forms (e.g. Herbam or Terram) in combination with Creo, healing wounds isn't such a big deal IMO.
Finally it is a question how you like to play your saga...... both makes sense IMO . It is up to you. And I prefer to have a possibility to get wounds healed without a big deal.
keep in mind that the healing wall is very controversial, not because of the belief it cannot be done, but because of the belief that the effect should not be permanent and uses a momentary creo ritual to overcome the limitation that muto spells cannot be permanent (in a book that is all about changing how magic affects the setting and suggests other possible changes). It is still, however a weak example due to that controversy.
While not muto, there is also the effect Vulcan's Favor (MoH, p.32) which is a CrTe effect that constantly repairs the enchanted item.
The way the muto "self healing wall" effect from TME works is by giving the wall the self-healing ability of a human/animal/plant (depending on form requisite). It is important to remember that the spell is still primarily a CrTe spell, with the requisites contributing to an unnatural feature of the wall.