By your argument I could do the same with MuAn (assuming a leather bag) then, changing the bag so that the inside is one hundred times as large as the outside, right? No need for a fancy mystery, no requisites, and a magnitude lower. Hmmm, I'm convinced. I had never realized Hermetic magic could do this sort of stuff.
Incidentally, weight is still going to be a problem, though obviously other spells can obviate that.
I think the "wood outside/bronze inside" was emphasizing that the glamour is making the inside, the bronze, look bigger, but doesn't change the fact that the outside, the wood, hasn't changed sizes.
I think it's your reading/interpretation of canon that is not being accepted. It's quite possible you are reading it perfectly correctly, but it's such a jump that I (and others?) are having a hard time making that mental shift in our understanding of "what's possible". Because magic cannot create Regiones, and that's exactly what it seems you've accomplished with this interpretation.
It seems to break an unwritten law that you can Glamour something to be physically larger on the inside than the outside - not just appear to be, but actually, physically measure larger.
I can easily see how a tent could appear to be bigger on the inside - the occupant moves around, and believes it's roomier, even if it isn't - it's all in their mind, their perception. But I'm not sure you could put a length of wood into that tent that is bigger than the previous dimensions and not rip the side of the tent. (How do the rules read on that?)
Let's say you have a bag that holds 1 cubic yard/meter of stuff. And you Glamour it to be 10x larger. Then you pour in 10 cubic y/m of grain. Is the grain fooled by the glamour? Does the grain fit because it perceives the bag to be roomier?
If a magi climbed into the "larger" bag, and set up a table and chairs, and then cast a big Intellego spell to see through high-powered illusions, would they then get crushed because they suddenly see that there is not room in a 1 cubic meter bag for all that?
Maybe briefly quoting only the relevant parts of the rules might help for those of us who are unfamiliar with this section of the rules.
As for the Muto effect "highly unnatural change", that's purely up to SG/Troupe interpretation, and there is no "right/wrong" on that. (Seems a bit extreme ims, but that's just mine, not yours.)
Well, Hermetic magic plus a major mystery.
Chris
I think I can quote this much without copyright issues:
It goes on to say that you might have to crawl inside it to find things. I really don't think I'm misreading it. It seems pretty straight-forward.
Also, you seem to misunderstanding Glamour magic. The illusion becomes reality. So a glamour of a fire can set wood on fire and a glamour of an axe could be used to chop wood, even if the wood has no sense of sight/touch/etc.
Chris
Itâs not so much a misunderstanding of glamour magic, as itâs a whole new added facet to the mystery. Nothing in Glamourâs four paragraph description in Mystery Cults suggests in capable of such an effect. Yes it says that a glamour behaves as an actual thing, it can do damage, has weight, and mass. But adding empty space is unmentioned, and to me an unexpected addition to the medieval paradigm.
Donât get me wrong I accept that itâs valid for glamours to create illusory spaces. Pictures you can step into and mirror doorways are fairly well represented in various stories. The effect is also unequivocally described in a published book and therefore in my mind part of the RAW.
To Me thatâs the cool part of Magi of Hermes. I personally feel the writers and the editor where careful about what was put into the book. Itâs chock a block full of examples of how magic can be used in interesting ways. Many of witch clarify and even expand what we think hermetic magic can do.
That's not the part I referred to about the misunderstanding. The whole thing about perception causing glamour to cease to be real and only become illusion is the part I was referring to. Perception does not change glamour from real to illusion. Without this misunderstanding, where does the statement about being crushed because of the use of an InVi spell arise?
I agree that the use of space is a new facet, though not one that was ruled out. Once I saw that use I realized it really fits the idea of a road that never gets you to the destination and things of that sort. Those may just be modern ideas of faerie things, but I see how it fits them.
Chris
Why didn't I think of the picture?! I even told a story based upon that idea. Silly me. Thanks for the idea.
Chris
No, Hermetic magic without a mystery. Level 5 base MuAn: "Change something made of animal products in a major unnatural way". Thus changing a normal bag into one that is 100 times larger, butonly*inside. Ultimately, if you can do it with glamour, you can also do it with plain hermetic magic.
The basic question - the answer to which, as Chuchulain pointed out, is very saga dependent - is what kind of "impossible" effects we allow in our sagas to exist atall*? Can space be warped so that something is smaller outside than inside? Can space be warped so that two or more identical bags share the same "inside"? Can an item simultaneously exist and not exist - so that a bag exists for the caster and for its contents, but not for anyone or anything else?
According to the RAW, there is no prohibition against such effects even in plain Hermetic magic. The question is whether their results are compatible enough with reality that you can live with all the paradoxes they create. If they are, well, they are already inside the scope of hermetic theory. If they are not, there's no mystery that will allow you to achieve them. I think it was saint Anselm who boldly claimed that not even God could make 2+2 equal 3.
While they are certainly strongly against the "physical" laws of the time (though they are not 100% against modern physical theories), if magic can turn your mind into a bird, why shouldn't it be able to make a bag bottomless? I've thought quite a bit now about the ramifications, and although they do have some (Mercere portals are suddenly easy!) they don't seem particularly game breaking. So in the spirit of "if it's not explicitly forbidden, it's allowed", I'd allow them in my saga - especially because, as callen pointed out, they are now canonical 
I would say that i don't agree with you. I see a big problems to "space magic" : the medieval paradigm. But i'm not fan of D&D ideas in Ars ^^
A lovely application for that is to connect two or more books(or wax writing boards for easy reuse) so that anything written in one shows up in the other(s).
I would say that to go against essential nature of everything.
As long as you dont make it too easy i think it should be fairly ok.
I would slap on some additional magnitude modifiers on that though, for one thing, a +2 size modifier for that 100 times larger inside at the very minimum. And i would say the base effect is well beyond "major" so another 1-2 magnitudes there.
Why? Plenty enough of old myths and stories that includes things like these, meaning that its already part of "the medieval paradigm".
What says its a D&D idea? Where do you think THEY got the idea? They certainly didnt invent it.
And moreover, if it suits your game, who cares where you borrow it from? D&D has lots of both fun and good ideas, no reason not to make good use of them if there´s a reason for it.
Note that being against essential nature doesn't mean that you can't do it with Hermetic magic. Muto magic is precisely and explicitly for making changes to things that are against their essential nature. It is just that the thing reverts to its essential nature upon the expiry of the effect.
I'd buy that. Seems like a really clever use of the guideline, to me.
I don't think you really need extra magnitudes either --- unless you were making a really vast on the inside. 100x bigger seems fine at the base effect. 1,000,000 times bigger probably needs some extra magnitudes.
Oh certainly. I meant it more in the direction of going TOO FAR, so far that it probably couldnt be done at all.
Consider it a while first, with a base of only 5 and you´re still willing to give it free size bonus? And where should the cutoff point for free be, and why there?
Although i dont reject the idea, im also aware how much trouble easy access to this idea could cause.
If at least you have to "pay" for the size increase you get, well at least you cant make yourself a few pocket kingdoms to carry with you... "look at my pretty hat talisman, divided into several parts, this compartment here leads to where we have the city of hats´r´us..." :mrgreen:
What's wrong with that?
For starters, who needs regiones?
And please dont tell me you dont see pitfalls in having a pocketfull of cities with you all the time?
Want a large ship with you? Just shrink it long enough to stuff it into the "magic bag". Stuff the crew there as well while you´re at it.
With size magnitudes from the start, that will require serious investement into the item. Giving free extra size, well maybe you missed my post about making a Mystical tower with a more serious focus on size instead of complexity... Even with guidelines as they are, its not so difficult to create a multi-km high tower with a base of a few hundred m squared.
Sure, doing it as X times bigger than Y adds Y as a restriction, but if Y is something BIG it quickly becomes a serious problem, and if you spend lets say 9 or magnitudes, even a small item can start getting troublesome.
Sure, I can see that there might be some problems with this happening if it is the sort of thing that the troupe doesn't want to happen.
On the other hand, I don't really see that there is an inherent problem here from a story perspective. If that is the sort of story you want to tell. In fact, it seems to create a lot of new story opportunity.
All you have to remember is that if it's possible for the Players, it's possible for the NPC's, and the BBEG is sure to have taken it to a whole different level.
There is nothing a PC can do that is so "large" that it cant' be countered - or if it can't, then the SG made a really bad decision loooong ago, and didn't think about where it would (inevitably) lead.
(Every played Amber Diceless? Pocketful of cities is peanuts, and yet the PC's never seem to be as comfortably large as they'd like.) 
There is nothing wrong with any level of play, high or low fantasy, limited or unlimited, so long as the SG has made the decisions thoughtfully, and hasn't painted themselves into a corner. (And we've all seen that happen too often, which is why I always preach caution over "wide open" rules interpretations. Nothing "wrong" with it, just dangerous without forethought.)
You know, I could swear I had written something specifically suggesting this sort of thing as an application of Glamour, but I couldn't find it in Mystery Cults, and it wasn't in RoP: Infernal (Phantasm being kind of similar to Glamour). I can't think where else it would be. Maybe a post on the forums?
I find it charming that there are things that just don't fit well into the technique and form layout developed by Bonisagus.
Things that are bigger on the inside than the outside, shadows dealt with as entities rather than as the absence of light, control of fortune, these are not impossible things to do with magic but they aren't things addressed by the order's magic.
The fact that it is more complected to deal with cold than it is to deal with heat, the fact that you can create ice with creo terram or creo aquam rather than just one; these things make the order of Hermes magic more real to me. I love them all dearly
Right up till the point where one of my players wants to play a magus with a magical focus in shadows and I have to either twist the rules or tell him no, neither being ideal choices.
Why? It seems clear to me that a Magical focus is Hermetic in nature. All it does is double an Art score. It doesn't do anything for non-Hermetic stuff does it? A player can focus in "shadow", but he will find it less useful then he might of hoped. Now he has a goal for Original Research. What am I missing?
You're missing that it isn't fun for the player to have a magical focus that is a pain in the ass to use even when it is applicable and causes digressions about the nature of the target whenever he wants to spont a spell with it.
edit , that was harsh, what should have said was: "Yes I agree that the rules allow it, however doing things like changing shadows into semi-corporial servants that do your bidding or transforming yourself into a shadow don't fit easily within the system because it doesn't typically treat shadows as tings but rather the as lack of a thing. If I had a player who wanted to have a magical focus in shadows, I'd alter how I presently have the system apply to shadows in order to make a more satisfying experience for the player."
I apologize for my insufficiently civil initial post.