This came up while I was adapting my freeform RP character to Mage, and it turned out to be the clicking-point for me really understanding the game in full and appreciating it on the same level that I love the oWoD game's metaphysics. At the time, I was trying to squeeze her into the Acanthus Path because all the whimsical themes and imagery and laid-back trickster stereotypes about the Acanthus path fit her pretty well; She was in fact originally a Changeling character back in the day. The primary Arcana, however, were slightly problematic. She is, as a freeform RP character, a type of psychic whose abilities worked in the telepathic/astral direction- Half the rotes from the first two dots of Mind and Spirit could express most of her abilities elegantly, and these two Arcana had closer ties to her concept than Fate or Time. I could excuse having Fate and Time, of course, but not with the degree of emphasis that Primary vs. Common Arcana dictate. Maybe I could fudge it a bit by giving her (eventually) either the Pygmalian or Imagineers Legacy.
The problem was that I was focusing too much on the imagery and personality typified by the book's descriptions of the Paths, not on the paradigm embodied by the Realm and expressed by the Primary and Inferior Arcana. I avoided Mastigos because the imagery of Pandemonium was all demons and hellfire and iron chains. What she is now is in fact a Mastigos Imagineer, and to get there I had to interpret the Paths in terms of the paradigms of reality and magic they implied through their Arcana.
The Supernal Realms are supposedly worlds of Platonic Truths -- Each one embodies a different, but complete explanation of Why Things Are, in contrast to the Fallen World where everything is vague, arbitrary, unknowable and besides all that just plain broken. Maybe it works as a harmonious combination of all five Supernal Realms' paradigms; It's a silly idea of the limited human mind that there can be only One Primary Truth, and any attempt to describe reality will always always find both compelling evidence for it and against it. I think this harmonious combination is the way the world worked before the Fall, and everything that happens now is more like metaphysical inertia, the chicken that keeps running after its head is cut off. This decapitated chicken is important, but I won't get back to it until the end.
The ten Arcana are the different factors which make the world tick. In the Fallen World, where the Supernal Realms used to convene their influence, the Arcana work with equal potency. Each Supernal Realm has its own take on the Arcana though, manifesting their paradigm via a primary pair of Subtle/Gross Arcana and an inferior Arcanum. The primary Arcana represent the same metaphysical principle, as applied to the more sublime or abstract level of reality and the more apparent outer-worldly interpretation of the principle. The paradigm also has an Arcanum whose existence in that realm is a total illusion -- While the common Arcana are pieces that play a part in the world of the primary Arcana, the inferior Arcanum in that world is a laughable concept that only something as banal as the human mind could be foolish enough to mistake for being Something.
I'll start with Arcadia, going in the order of what paradigms I can describe most elegantly first. The key word for the Acanthus paradigm is Narrative. There's a nice little key word for each path made up by various people in the forum, and I find them thematic enough to scribble them in on each Path entry in my book. In Arcadia all the world is a Story, and while we all know damn well that the medium of this story is a role-playing game, from an in-character perspective we don't have to conceptualize 'Story' in terms so limiting as 'game' or 'book' or 'movie,' though individual Legacies might build on one of these more specific mediums. In the Narrative, things are put together thematically. The world is run by its aesthetic appeal, and although Abyssal tentacle-rape might not be very 'aesthetic' to your character, it fits the thematic criteria of Arcadia and its gods, if there are such things as Supernal gods. True Fae, anyone? The Arcanum of Fate deals with thematics. You can sense the world's aesthetic tastes with Fate, and thus hazard a guess at the flow you're supposed to follow, or tangle with it, trying to pull up other themes and placing them in such a way that Fate will follow those paths instead. The worldly manifestation of Fate is the Time, where our human point of view sees events lined up in order, this happening then that then that. Someone better versed in the Time Arcanum understands though that the Narrative is not linear, like a book. It's more of an improvised thing, like a Choose Your Own Adventure or, dare I say, role-playing game. The themes play out, but circumstances can change and things can be rearranged differently and still be aesthetic to the universe. And even free will, if there is such a thing, is limiting because even if we can choose from myriad paths, we're still only tracing one line. Maybe every possible story actually does play out, and movement in Time is more like movement in Space where you're just choosing which part to look at, rather than actually shaping your future. Think of the Time 3+ magic which lets you hop backwards a few seconds and redo your last action. Maybe you're not actually going backwards in time, but sideways to a temporal location that branched off a few seconds ago and is thus close enough for you to still reach.
The Common Arcana of Arcadia are not its driving principles, they are merely the pieces in the game which are manipulated. They still exist, but they are the Who/What things happen to, not the Why and How things are happening. Forces is the inferior Arcanum. Physical laws, interplays of energy and math have nothing to do with the way of Arcadia. Any consistency one finds in terms of physics is only something that has been narrated to maintain suspension of disbelief; A good story has a degree of consistency that lets people read it, but as any role-player knows, Fun and Story always trump the mechanics. Really, "OMG antimatter annihilation reaction!" uses just as many letters as "This energy-saver bulb uses eight watts."
The Mastigos paradigm is Perception. Everything is about point of view, both in terms of who's doing their own limited form of observing and thinking with Mind and what small fragment of the Tapestry their interpretation is even filtering information from with Space. Everything you know is (as far as you can ever know) subjective, both what you see and what you make of it. Everything is an idea, as malleable as you can convince yourself it is, and if there's anything approaching an objective world, it lies in the ideas passed between all these different minds; their Correspondence, if you will. Reality is a series of tubes! A well-versed mage knows that his mind is the surest place he knows might exist, and it is her prerogative to master that domain. And that's gonna take some work, 'cause you've got some major issues. If there is a world outside your mind, you're only getting bits and pieces of it, and thus it is also essential to mobilize your point of view to encompass more and more of the whole. Understanding Space and performing sympathetic magic, one overcomes the illusion that geometric distance is what separates objects. Distance is a matter of how much two thing affect each other, and you know that although oceans may come between you, you will always be far closer to your lover than that asshole holding up the line in front of you at the store. The mapping of correspondences in the external world is analogous to the thoughts and feelings constellating in your head, and an understanding of the psyche has little to do with mapping the folds of your grey matter. Distance is a spoon.
The inferior Arcanum in Pandemonium is Matter, that heaviest and most stable of threads. That something could actually exist as such, an actual stable form existing axiomatically regardless of anyone's thoughts or observations is alien to the Mastigos approach.
The Primal Wild is all about Evolution. Let's make a simple assumption: That which exists is able to exist; That which is unable to exist doesn't exist. Everything that you see around you is made up of the resources at hand, and the resources used for one purpose cannot be used for certain other purposes at the same time. Thus, every arrangement of things, whether material or ephemeral, is in competition with other arrangements. The things which keep existing does so because factors were stacked in its favor, and they are now competing with other things that also had the situation stack in their favor. Resources will thus naturally fall into certain forms which are capable of allocating those resources for itself, and after some time these forms will reach a degree of sophistication where you could consider them as being 'alive.' When searching for extraterrestrial life, it is important to remember that the criteria for life involve organization, not carbon and water. Life can be made of anything from dirt to plasma to memetic complexes. This is the nature of Spirit, evolution's principles as applied to rarefied resonance-substance and as applied to material threads, which become Life. There's a bit more to this, too, because there seems to be some kind of drive pushing evolution in ways faster and stranger than mere chance and logical elimination can account for. I've felt this drive in my heart, and damned if I can do a thing to articulate what it feels like, but it has more to do with the Thyrsus paradigm than anything I could type here. Language is Mind stuff, anyway.
Mind is the inferior Arcanum in the Thyrsus paradigm, a fanciful illusion created in a system which is truely run by the same inevitable ectropic drive. Your brain is just a computer running increasingly sophisticated software, the basis of which is the interaction of millions of instinctual drives. When the body is pushed forward by the drive of the Spirit, the mind is only an incidental vibration of the air from the impact.
The Moros best understand the nature of Transition, for Stygia is the realm of Death, which teaches the inescable lesson: This, too, shall pass. The ending of a thing, of course, is not the end of its constituent parts; They arrange in another form, then another, then another. When you die, you shed the weight of sin on your heart for these things carry meaning only within the transitory context of your life. In the World of Darkness, the burdens of a person's soul leave an imprint on the world, the ephemeral pseudo-entities that are ghosts. Everything that once was a person, in body and mind, breaks apart and is absorbed by the rest of the world. Matter is the worldly manifestation of Death. Life has gone to inert substance, without Spirit, just a pile of heavy resources waiting to be picked up by the next system. The Moros knows that even the planets will some day crumble, and can express the mutable nature of the most stable substance through their Arcanum of Matter.
Is this what is happening to the Fallen World? Is the Abyss part of a reality even greater in scope than even the Supernal Realms, and the horrible decay we see all around us is just decomposition on a cosmic scale? Sympathising with the Abyss in this way is futility and madness. We are beings limited to our own world, and the Abyss is not our friend. If there is a greater purpose for the end of the whole Tellurian, it is on a level too abstract for us to hope to really understand, separated by a metaphysical distance which makes nothing of Eternal Hell. Do not dwell on the Abyss.
An Obrimos has seen the world as a Mechanism of cosmic scale. All the threads of the Tapestry possess energy, motion that carries them to collide with each other to deliver that energy on from impact to impact. If one could comprehend the whole of the multiverse, they would see that it all fits together in a most elegant, logical mechanism. In the Aether, the Obrimos observes how the world orders itself from the smallest motes of light transferring from particle to particle to the great motions of the planets and stars, both their physical bodies and the spiritual principles the represent. The Arcanum of Prime controls the Mechanisms by which magic and, indeed, all the grosser components of the Tapestry interact, as the Arcanum of Forces controls those various energies which compel worldly substances. The Empyrean is Perfect. There is no loss, no Death, for everything is part of the same eternal Principle.
The images of faeries, demons and angels are just common allegories one uses to describe the Supernal Realms in terms of 'supernatural' archetypes which we're already familiar with. One shouldn't think twice about the images of the Supernal given in the book as long as one can grasp the thematic essense of the realm.
A Legacy is a more defined take a person builds onto their paradigm. To craft your soul requires developing a system of magic with which you can touch the world with greater certainty. Indeed, the crafting of a soul is the crafting of an inner world, and the more you define just what your soul is the more reality it has. This shows in the powers you learn to perform without Paradox, the ways you gather mana with greater ease, and the integration of new Arcana into your primary system. I believe that this is the reason the world even made such a thing as mages, because even if the world has already been killed, even if there is nothing anyone could do to save it from the encroachment of the Abyss, every mage is a budding universe unto herself, and Ascension is a path which can go beyond even the Supernal Realms, something more important than the achievements of the archmages or even the Exarchs and the Oracles.