For what it's worth, here's a brief explanation of some of the more esoteric worldbuilding behind the main novel idea I'm working on in the background:
Basically, we're talking non-standard fantasy world that's part of a linked network of several score worlds, centered on an artificial hub-world. The one we start on is in the majority, in that it's fairly isolated from the greater scope of things--the only people who are really aware of any sort of significant detail are major leaders, off-world travelers, and magic users with enough power to earn or make a ticket out of Dodge.
On the nature of magic itself, I'm intending to make things more interesting by not using a specific codified system. Or rather, not using a single system. Magic is as much art as it is science: art in the sense that all of the different paradigms work, more or less; science in the sense that users of various methods have codified much of their knowledge, though by and large knowledge is hoarded or lost, due to the lack of anything more than regional guilds that facilitate master-apprentice relationships.
I've broken it down into several general classes of magic user: Channelers, Casters, Contractors, and Constitutionals. These work like this:
Channelers hone a metaphysical organ, (either present from birth or artificially created, depending on the individual) which allows them to tap into a common, functionally infinite source of energy that exists outside human perception of reality. Their "strength", "endurance", and "control" regulates how much power they can draw on without burning out, how long they can maintain their draw without exhausting their bodies, and how well they can direct their power.
Casters develop personal energy reserves through extensive training, and are capable of using anything from the smallest trickle to their entire reserve in their magic. They tend to be the weakest of the four types of magic user in the early stages of development, as their primary limiting factor is the level to which they've developed their own power; they have to work for every scrap of energy they have, but also have a much easier time using it, as it is quintessentially them.
Contractors make pacts with just about anything that's willing that has some sort of magical power. Typically the nature of the contract changes depending on the relative power of the contractor and the contractee; a minor spirit of something-or-other might accept a binding from just about anyone without conditions beyond shared senses, but a powerful entity could require things along the lines of periods of possession of the host's body, physical or mental changes, certain types of behavior, etc. The nature of this is in the trade-off: the more you're willing to sacrifice, the more power you can gain. It's a quick and dirty way to power, and the strings are always there, even if you can't see them. Contractors who survive long-term can end up making permanent bonds with their contractees; this often involves a true melding of minds and personalities, but is rarely done between anything but the most powerful individuals.
Constitutionals are, put bluntly, sorcerers. Dirty bastards who were born with power. They're often born into families with traces of blood from nonhumans, and to those living in areas richly charged with energy. They're something of an amalgam of Caster and Channeler mechanics; they generate their own power at a constant rate, but can't store it outside of a spell matrix. Magic for a Constitutional typically involves either many low-cost spells or longer buildups to strong ones.
Classes aside, there are also the methods of application. In other words, the way that a magic user expresses power, regardless of where it comes from. To an extent any user can manipulate their power freely, regardless of where it comes from, but the power dropoff from this makes it prohibitively inefficient for most tasks and for all but the most powerful users.
Some make use of linguistic potential, either with script and runes (which can vary from tattooed spell matrices intended for repeat use to rapidly applied brushwork to what are essentially pre-made ofuda--albeit with a much wider range of materials), or with spoken words--mnemonics, magic words as we think of them, systems of interchangable syllables that act like verbal magic legos. This crosses with another sort of matrix: musical patterns. These can be sung, played on instruments, hummed, whistled, or simple patterns beaten on whatever happens to be handy.
There are also the various uses of body language; dozens of personalized systems of gestures intended to evoke specific effects, essentially a counterpart to the "lego model". This also relates to the use of foci (as do the written systems; physical objects are excellent holders for runework or script, though plain metals, gems, and certain other materials can also store energy patterns).
That's basically what it all comes down to. You've got a world (somewhere down the line in potential sequels, many worlds) with no single codified system of magic. Instead you've got four major systems (that just counting the ones the mortals of this particular world have created) and virtually as many different patterns for creating spell matrices as there are magic users. There's no inherent meaning to any of it, only that created by the user's mind; power is shaped because the user believes that it will be. This should feel genuinely chaotic--that's the point: there's no rote standard for users; no "Oh, we're in a fight. They'll throw balefire/a stunner/whatever, I'll answer with balefire/a shield/whatever." because nobody has the slightest clue how other users do anything with their power without observing them for a while.
Which is where we arrive at the really fun stuff. There are all these people warping the stuff of reality with what amounts to a physically manifested form of willpower--a lot of stories talk about willpower in relation to magic, but I mean it literally: all magic is powered by the belief on the part of the user that the laws of physics should sit down and do as they're told, and it works. My intent is to portray this as both utterly ordinary (given that it's the norm there) and completely fucking terrifying, because the whole time the plot is winding up and running down, the world in the background will be continuing the long, long slide towards ripping the veil asunder and all sorts of insanity from understanding what this power really is and what the hell is going on with the universe.
Obviously the actual plot, characters, and a lot of the less metaphysical elements of the world are going to remain snugly in my pockets, getting mixed up from my notes for all the unwritten crossover fanfics.
Hah. Brief. Thoughts?