Cheesy or not, I still find this interesting from a theoretical point of view.
Consider the following spell:
Feed on the beast’s vigor
Mu(Re)An(Co) 40 (25: Give an animal a magical ability, Touch +1, Momentary, Individual, Change an animal into a human +1, Completely control an animal +1)
Gives an animal a magical ability equal to the spell “The Gift of Vigor” and force it to use it on you.
Giving an animal a base 15 ability should be possible with the 25 MuAn guideline, the ability has a ReCo requisite. I am not sure if animal and corpus fatigue is “compatible”, so to be sure we transform the animal to human form (MuAn[Co]), eventually we add a similar affect to let the fatigue be tranfered from animal form to corpus form. Either way you can still control the animal by ReAn since it gains no human soul or mind.
Vim requisite? As far as I understand the guideline only call for requisites based on the ability. Should there be a Vim requisite anyway? (Clearly a magical ability, but the guideline already account for this?)
There are two suggested ways to make sure animal and corpus fatigue are compatible. The first (transform the whole animal) could hinder the animal to use the ability given. The other is not completely “baseline” and should maybe be given an additional magnitude form changing/part effect?
Expanding the possibilities:
Is animal fatigue compatible with corpus fatigue?
If they are not compatible and both the suggested ways to make sure it transfer are ruled out, this could still be used in heartbeast (or other animal) form? (Also reducing the spell level by 5 to 35).
Give this ability to your familiar?
Reading the guidelines making severe transformations to humans is about 2 magnitudes harder than with animals. Could a 35 base be plausible to make a similar spell (grant magical ability) affecting humans? This would result in a level 45 Mu(Re)Co(Me) or Mu(Re)Me(Co) spell. Should changes like granting magical abilities be allowed for corpus at all?
For a level 40 spell? Not much problem, really. It is the level of spell that can grant you archmagehood (and require you be an archmage in the first place to be able to cast it effectively in a lot of situations ) so no biggie at all. It already existed (Triamore, 4th edition, Hooks chapter, even if at the time it had a different name), so it is not ground breaking
It could be argued that you cannot transfer Animal fatigue to a human, but you can do the same from a grog.
But if you want some fuss, yeah, let's argue that you cannot transfer vitality between Forms. There, problem in your dish since there is a fundamental flaw in your approach. You can transfer vitality between humans, even between men and women, but not between an animal and a human since they are fundamentally different stuff in base matter.
With the spell "Gift of Vigor" already being commonly available without any restrictions I don't see how this will require uniqe research, at least not to use the more "straight forward" version while in heartbeast from.
Any muto spell to change the form will transfer current fatigue levels from one form to another, so other variants of this spell should work aswell, but some extra research requirements are plausible.
Unless there are some rules I missed about spesific muto changes being "too severe" for corpus magic, it should be possible to device a spell working between humans. It will probably require some research to invent the coprus effect based on the animal guideline (grant magical ability, should result in a 30 or 35 co(me?/vim?) base).
Slighty related (for a friend's magi theme): are there any "blood magic" life/fatigue/wound steal related breakthroughts described in any official books?
Break it into 2 spells:
1st spell is D: Ring, T: CIrcle and does all the Muto stuff
2nd spell gves you control of the beast and can be designed with a variety of parameters.
(3rd spell keeps the blighter in the Muto Circle but might not be necessary)
I just now noticed though, that you have a Momentary Muto spell - what do you expect from that?
As said above, make it an "humans only" feed. No feed from animals, but yes to feed from your nearby grogs. Makes for a quite creepy magus of vampire inclinations. Quite cool, in fact. And feared by nearby covenfolk.
The Gift of Vigor specifically mentions that this is the closest magi have come to restore their energy in order to cast more spells. And the description is quite clear that it transfers energy from the caster to the target. If it was currently possible to do so in the reverse direction using standard hermetic magic, the note would not have been included in the spell's description.
Furthermore, if you look at the Limits of Magic (ArM5 pp.79-80), more specifically The Limit of Energy: "Hermetic magic cannot restore one's physical energy (Fatigue Levels)... Most magi think that this is a flaw in Hermetic theory." To me, that is a clear indication that further progress in the transfer and restoration of energy is a subject of Original Research. I don't have HoH:TL with me right now, but it may even be mentioned there in the section about Original Research.
I think that here you are mixing up what a MuCo spell is designed to do (transform the physical shape of the target) and how that result is represented in the game rules.
A MuCo spell does not "transfer energy from one form to another". The target of a Muto spell specifically remains at the same Fatigue Level when the transformation occurs: if the target was Weary before the transformation, it remains Weary after the transformation.
Please bear with me, I'm kinda just thnking "out loud" here, but others might find this interesting.
As far as I understand the original concept, the idea goes as follows
Use MuAn (base 25) to give an animal a "magical ability" - namely the abilty to donate fatigue levels via an effect essentially identical to Gift of Vigor.
This takes requisites of Rego and possibly Corpus, but not necessarily the later.
Because Xavi mentioned that you might not be able to transfer fatigue from an animal to a human, the spell then transforms the target animal into a human shape. Please note that the transforme animal is still an animal mentally, meaning it is not subject to ReMe effects.
That's MuAn(Co), base 10. Because it's chained together with the above effect, that's +1 for complexity.
I'm not entirely comfortable with this combination, simply because humans cannot be given "magical abilites" via MuCo in this fashion.
ReAn (base 15), completely control an animal. Order the animal to use it's new ability to transfer energy to the caster (effectively moving fatigue from the caster to the animal). Again, because it's chained together with the above effect, that's +1 for complexity.
Since the spell is momentary, the affected animal then immediately turns back into it's original animal form, only it is now more tired than before, as it has donated some of it's energy to the caster.
With loyal (/crazy) grogs you don't even need mind control
That is why I grant the ability to the target (who "in return" target you with its new gift).
As I see it the "limit" is already flawed/broken, but I agree that most ways to exploit this will require additional research.
I didn't find anything in HoH:TL about "fatigue" breakthroughs.
I agree that this is what the base rules imply, tho they are not specific about it. With that said, the MuAn(Co) effect is not supposed to transfer/move any fatigue (this is done by the ReCo effect [Gift of Vigor]). It preserves current fatigue, but change its form to make sure it was transferred. That being said I agree that using the Gift of Vigor between a human (Co) and an animal (An) might be a stretch, tho you could make a variant of the spell for animal to animal without need of original research (given the rule that you can translate any Co/Me effect to An used on animals).
Yes indeed Tellus, this is very much what I intended.
And yes, it could be divided into several spells, but it seems more useful the less preparation and time it takes to cast. After all, fatigue is only an issue if you are limited on time.
One more thought:
While "magical abilities" as a rule should be based on spell guidelines (imo), several fairies have the ability to "steal" fatigue levels without the restrictions the Gift of Vigor has. This should enable a mage with sufficient knowledge about fairies to grant himself the ability to steal a fatigue level (by granting himself a magical ability with a spell targeting himself rather than a "victim"), at least if the mage already has some fairy blood.
To make it more fully fit the rules, especially the text of Gift of Vigour, I'd enchant the effect into a ring, worn by a faithful grog and then have the grog (possibly mind controlled via the same ring) use the effect on you when required. Of course, you are going to want either meaty penetration or to lower your parma to have it affect you, but thats neither here nor there.
In fact I rather like this idea, in an evil genius way. Imagine a very evil magus, with a group of grog slaves, each bearing an enchanted ring that casts gift of vigour. They are under a group target mentem spell to control their actions and have otherwise had their minds scrubbed, making them near automatons. The magus could use his magic and when fatigued, get his slaves to cast goft of vigour on him to raise his fatigue levels. He could even have the grogs kill themselves doing this, at which point he could retrieve the ring and find new slaves.
Very nasty, if somewhat obvious and inviting trouble with the mundanes.
Even that, to me, might require some original research to accomplish. Because such an effect would already go beyond what Gift of Vigor does.
I repeat: Gift of Vigor transfers energy from the caster to the target. If it is enchanted into an object, who is the caster? The object, not the wearer.
So if you allow this to work for an object, you are allowing the transfer of energy between two targets, not the from caster to a target.
I will freely admit that I take a rather hardline stance with regard to the Limits of Magic. IMHO, they set down what can be done with Hermetic magic as it currently stands. Anything beyond that needs Original Research to improve Hermetic magic, or some form of non-Hermetic virtue (which is still incompatible with Hermetic magic).
Feel free to play it differently in your saga.
But by my reading, my position is supported by RAW.
I would suggest looking at Triamore book, page 74. No rules, but text describing basically what you try to do. Sap the energy of a nearby human. In any case since this is transfer energy from one being to another I do not see it as a breakthrough necessity: it is not restoring the energy, just moving it around. To me those are 2 very different things.