What spheres would be needed in order to create a layer of reality in a specific location that exists simultaneously with regular reality?

Question

I have been reading Demon: The Fallen, and one of the concepts there that really piqued my interest was reality being multilayered with the same thing reflecting differently on different layers. For example, when Lucifer and Mikael were fighting, in one layer they were actually fighting, and in another layer they were simply engaging in mental combat.

What spheres would be needed — and to what degree — for a mage to create interposing realities where multiple actions of the same variety are being performed? (e.g., A person within the area both reading on how to play an instrument and practicing playing it, or analyzing a certain enigma from multiple directions with the enigma being a literal puzzle in one layer.)

PS: Layers do not have to intersect between each other beyond the information being transferred.

Answer 1

It is going to be difficult for conventional levels of spheres to do that. Fortunately, the book Masters of the Art deals with high levels spheres (up to 9); on page 73 you have the 9th level of Prime as literally create a universe:

An Archmage at the pinnacle of Prime can also use Quintessence to create a pocket universe. The internal dimensions of this universe, and all other properties, are at the Archmage’s discretion; his knowledge of Patterns is the only factor limiting the universe’s internal properties. This pocket universe is a small piece of folded space where the Tellurian naturally balls itself off in a sort of protective shell. Naturally, watching this universe evolve can provide all sorts of insights for less-experienced fledgling mages, and it may even be an interesting place to visit for the Archmage creator. The mage simply gives the tiny Pattern a spark of creative force, and lets it run. Perhaps this is the way our own universe started...

As for the information transfer, that is usually Correspondence, although I am not sure to what degree you will need it to transfer a whole universe's worth of information (you will get some Virtual Adepts really interested here). But since we are already with arch-spheres, we could probably think of something like Correspondence 8: Limits of Spirit (on page 67):

Since the mage can easily create bubbles of space that share characteristics with other space — essentially co-locating spatial features instead of just objects [...]

The question “will that be enough?” is a good one, since, well, it is not stated that life exists on that new universe or any kind of matter. I it unclear if you will need to “put that in” so to say (but then again, does time exists in this new dimension? Do you need that? Does this universe have an Umbra if I do not use Spirit? And so on...)

As usually with Mage, my best guess is “depends on your Narrator’s interpretation”.

Answer 2

It depends on how "real" the new reality should be.

To quote Morpheus:

You can create a new, empty realm in Umbra with Spirit 5 (and probably a fair chunk of Prime), but it will be an empty place that you can eventually populate with creatures, including copies of people. But they will be copies indeed, not linked to the original: if the copy dies, the original would continue to live on.

The proposal made by @Random makes sense to create indeed a "real reality" that has its own laws, for example turning everyone "stepping there" into My Little Ponies with magic based on friendship. But that indeed is an enormous task, available to archmages with well over 5 dots in spheres!

But, what if you just want to make someone think that they are in such an alternative reality? For example, whenever they step up into a warehouse, they will start believing that they are indeed Ponies? Then all you need is Mind 4 (or 5 if you don't want them to ask stupid questions and go insane) and Prime (either 2 to let them interact with non-existing objects or 5 to make such objects real) and here you go: everyone inside the warehouse will think that he is a 4 legged citizen of Equestria, while anyone peaking inside would see regular people acting a bit weird.