how would you fine people give a wo/man a prehensail tail like a monkey magically?
I would tend to think Mu(Cr)Co(An) or something like that with T: Part. I think the Creo might be needed to add the body part instead of just changing, but I could be wrong. However, it is rather anachronistic. Well, I guess there is the harvest mouse. So perhaps as a fully prehensile mouse tail I could see it working reasonably.
On A&A cleared that any change of parts or way of a body is exclusively Muto, Creo is only to make for example a few sand to a mountain of gold for duration, for example. Any change that includes wings or something like that goes with Muto easily.
The spell guideline is Muto Corpus Level 2, "Change someone to give them a minor ability" -- exactly the same as Eyes of the Cat, p.131 of the corebook.Maybe this one could be renamed "Tail of the Mouse"?
But would this be a minor ability or a non-minor ability?
It depends the kind of tail your growing. If you can grab some objects or even hold your own weight, it seems minor. If it acts like a real third-hand (and gives a bonus to craft or even fighting), I would add (at least) a couple of magnitudes. I think that the Animal requisite is purely "aesthetic" and should not count.
If it's modeled after Troupe Upbringing, it should be minor. Having a 3rd hand is a lesser step than the Minor Flaw Missing Hand.
what about extending the tail bone?
bone, skin, muscle - all Corpus/Animal, all work the same.
The question of what is minor/more-than-minor for this MuCo guideline has always been a trigger for disagreement, so it's truly a yswv situtaion (where w = will.
If in doubt, use the Central Rule (p 111) - compare the result with that of other spells, consider the power-level of your saga and the preference of your players, and adjust it from there.
Actually, it's pretty much more than aesthetic in this case - it's like "wings", it's something distinctly non-Corpus that is being added, and so Animal would be a definite Requisite.
Any more thoughts on the subject?
My suss: It is not minor (like Eyes of the Cat) as the degree of mutation needed is larger. And would certainly require Animal as a Req, but not Creo.
So, MuCo 3 as base, to make it one degree harder than EotC, unless the tail was purely decorative then it would be ok as a MuCo2 (as that tail just sounds like a flap of non-functional skin and bone). By Monkey tail I'm assuming you can mimic all the things that a normal monkey tail can do (assist balance, gesture, and nudge things) which is why I'd make it slightly higher than MuCo2.
that's the general idea of this spell