Here is the concepts I started with when imagining magic in The Queen's Hound:
Artwork and music evoke certain reactions from people, whether they understand them or not. An american infant and an elderly japanese man can both feel excited or sadened by certain selections of classical music, for instance.
All over the world, we have similar mythologies. Ancient (in some cases, cave) drawings that could be said to depict "dragons" or "unicorns" have been found all over the world. Yeah, there's a lot of differences, but there's a lot of similarities, too.
>So part one of the theory (remember, this is fantasy) is that there is a "Common Human Mythology". This mythology tells us the difference between a sad melody and a happy jig, it says that red is a passionate color, and that dragons are creatures of power.
Have you ever felt someone staring at you? Have you ever seen someone weep and been overcome with their sadness? Or felt someone's anger towards you? I took this and the notions of "Putting energy out into the Universe" or "Vibes" and thought up part two of the theory:
>We are connected by an unseen web of emotions and energies that we are ultimately in control of.
Then I threw in a healthy dose of "Consensual Reality", basically considering the nature of our souls (powerful) and how, in the consensual reality theory, we've all agreed that in our earthly bodies, we'll play by certain rules.
>Part three of the theory: The laws dividing science and magic are there because we agree that they are.
Finally, I thought that, hey, there's all these people throwing around all this energy, and such a great number of them wish that they had more power than they do. What if so many of them wanted more power that the scales tipped, and our consensual reality shifted to allow "magic" on a grand scale. What if, suddenly, when you wished that someone would just die, you sent out that negative energy, and they really did die?
Then I brought the Common Human Mythology back into it. The Common Human Mythologies, I figured, are basically ways for us to conceptualize those energies we throw around, and therefore they exist on an "energy level".
The human body is an energy body as well as a physical one, so I figured there would be a limit to how much of these energies the body could contain, and this would vary from person to person. When that level was exceeded, well, the body would be destroyed. Then I thought that the intense release of that energy, now channeled into a form granted it from the common human mythology, would put energy out into the world strong enough to take on a bit of "life" of its own.
>Long story short, a person can summon negative, painful, killing energy and hurl it at someone they hate, but if the energy summoned is too much for their body, the energy will destroy the body and enter the world as its own entity (now that it has been given shape). This shape would likely be something dark and destructive...a black dragon, perhaps. Likewise, they could sincerely wish for someone to be helped or healed, lay their hands on them and will them to be well. If the energy was enough to destroy them, we may end up with something white, pure, healing...like a unicorn.
To keep all the magic straight and consistent, I wrote it all down in game terms, and ended up creating an RPG based on the novel. Both are due to be published later this year.
I would also like to say that while magic definitely plays a role in my story, it is largely part of the background and character development but not involved much with the actual plot. The world is post-apocalyptic because the birth of magic was so abrupt (and, well, led to dragons and werewolves, and all sorts of baddies) that it virtually destroyed mankind.
Imagine: rush hour traffic. Negative energy everywhere. Someone loses it, and the energies they send out destroy the guy who just cut him off, but the energy is too much, and suddenly there's the energy form of a dragon out in the middle of the street. Panic ensues...and the energy is just too much. More people lose control. It spreads like the dust of a mushroom cloud, and in the wake, powerful incarnations of fear and destruction, who then go on to create more of the same. Viola. The Apocalypse. Those who can control their energies survive, and the remaining humans have great power - and great restraint.
So I like consistent magic with definite rules, in high or low saturation. The "well, it's just magic" thing always seems like a cop-out to me. Harry Potter avoids this to some extent because it introduces the magic (usually in one of Harry's classes) long before the magic is needed in the story. What I don't like is when you are operating under one assumption (oh, no! They're trapped and there's nothing they can do!) and suddenly, ah-ha! Magic! They're saved!