Are there any sources of Muto Corpus guidelines beyond those listed in the core? There are so few in the core that I feel like I don't have a good base to extrapolate from. I'm especially interested in guidelines that don't require a requisite. At the very minimum, if anyone has suggestions for what level granting a 'major' ability should be (as an equivalent to the grant minor ability guideline), that would be awesome.
ref: atlas-games.com/pdf_storage/ ... elines.pdf
For MuCo it adds:
Level 5: • Add or remove human body parts from the target in such a way that he no longer looks
human. These parts are normally functional, although a spell may be deliberately designed so
that they are not. The Target is Part, not Individual (although Groups and higher Targets work
as normal). [MoH p.49]
Adding one specifically for MuCo isn't what you are after, but there are other FoTe combinations that might apply. ie. Look at some of the MuAn guidelines for ideas too
Adding a major ability - I'd take that on a case by case basis, considering what the ability was. Default of an extra +1 mag, but if the major ability is nearer to one of the full transformation guidelines, then go with that (transform to water).
Do you have an example of what you want o do? I've drafted a few house rule MuCo effects.
I don't have my books handy but I believe MuCo 25 allows a magical ability like breathe fire or fly. I'd argue those are "major" abilities.
Rich
If I can permanently make myself be able to breathe fire, I'd like to know how to do so..... the MuCo guidelines don't really mention anything like that.
I've seen no such guideline that allows one to breath fire with MuCo. In fact, there isn't even a guideline to turn into fire...
MuCo is hard. And it's made harder by the need for requisites. An ability to fly would almost certanly require an Animal requisite, as no person can fly, and to breath fire, it would require an Ignem requisite.
Now, MuCo is awesome at improving soak, and you can make your grogs very tough.
To me become fire s like become air or fog.
Sorry, just looked in the book. Page 118 "MuAn 25: Give an animal a "magical" ability, such as the ability to breath fire (requires a requisite for the ability)." Therefore MuCo by analogy, whatever level that works out to be.
Rich
The basic effect is the guideline noted above, adapted to Corpus instead of Animal. Muto spells cannot create permanent change. However, you can enchant the effect into an item - preferably the familiar cord, to avoid Warping - and so have the effect be permanent. Alternatively, you can use Mysteries such as The Bjornaer's Inner Heartbeast-Anima to change your essential nature permanently.
Where do you get that mu magic can't affect permanent change? It should require vis, certainly, but I think either I missed a sentence or there is a misunderstanding...
It is one of the Limits of Magic (p.79), The Limit of Essential Nature: "Thus, Muto magic must always be maintained, while the effects of Rego magic persists after the spell expires."
And since the longest "maintained" duration is Year (which requires ritual magic, thus raw vis), Muto magic cannot directly affect permanent change.
Of course, if you transform stone to water, it will splash down on the ground, so that when the duration ends you will end up with pebbles. But that is a result of the environment, not the magic.
There is no D: Permanent in the 5th edition. D: Momentary causes a change which only lasts for a moment.
Creo can cause something to appear and become real if cast as a ritual, but this works specifically for Creo.
So no, currently Muto cannot affect permanent change in the current edition.
Ah, I had thought a muto ritual could cause permanent changes, but rereading the section it is apparent I misunderstood.
I see lots of circular tattoos in the future. Target individual duration ring...
Wouldn't the target of the Ring be outside the bounds of the ring?
Maybe it's a REALLY big tattoo around the character's waist, and the target of "Part: liver and/or stomach".
...OK, I got nothin'.
EDIT - OK, I suppose you could target someone's head with a circle-based crown of some sort.
But yeah, once you start getting into movable circle enchantments, the inevitable result is Star Trek inspired carts, with ring/disks enclosing them. so that you can create magical shuttlecrafts with magical shields and warding effects.
Which was fine by ME, but no one else IMS felt that was genre-appropriate. 
Certainly a YSMV thing.
Circles for duration do not need to surround the target, that is only if ring is the target. I can cast a spell with target boundary and duration circle and as long as the circle isn't broken the spell remains. Just because they typically go together doesn't mean they have to.
Granted it is an assumption that the item must be wholly within a circle to be a valid target. A reasonable one if the target leaving the ring breaks the circle.
Edit, fixed munged quote.
Yeah, it isn't very clear but my reading too is that the target needs to be in the ring.
A target which was not within the circle at the time of the casting would not leave the circle.
Besides which, as written if read as literally as you suggest something with target ring duration ring could never be broken, except by physically breaking the ring, as the ring will not leave itself...