As promised, a bit of an explanation of magic in the PhoenixFeathers world:
There are two factors which affect the ability of an individual to use magic, referred to as 'touching the aether' and 'channelling'.
Touching the aether is an inborn ability and usually manifests before or during puberty. Maybe 40% of humans have it; 60% of elves; 100% of faery. Beings with this capacity can touch the aetheric plane and control and manipulate forces generated there. Ideally, one would use one's innate magic but in reality few races have sufficient natural magic to use this way. Fae are one race which do have plenty of innate magic, due to their racial heritage. Because of their general lack of internal power, humans have developed an alternative way of using magic which draws on power around them (see below for power generation). Most races have followed this method. It involves opening a path to externally generated magic and pulling it inside oneself to use in the spell, and is called 'channelling'. The power level or gate rating ('gating') of a mage is the rate at which they can pull in power, often known as the width of their channel. Channelling and touching the aether are both things one is born with or without. Most people who can touch the aether can channel some quantity of power, but for many their channels are quite narrow; they have a low gate rating. Some people can touch the aether but not channel, and this is a cause of great frustration and often leads to harm, of themselves or other people. A very few people can channel but not touch the aether; most never find out about their abilities but some have been greatly abused by magic-users since they almost invariably have wide channels with strong protective walls, and are good for channelling lots of power. The linking between a mage and his channeller is irreversible and can be terribly abusive although great partnerships have also been formed.
Channelling can be done through alternative methods - one way that many biowizards once used is to make use of a familiar to help one channel magic. The familiar is linked to the mage (in a similar way to that of a channeller to his wizard) and acts as another channel in addition to that of the mage. Birds are common familiars since their air is opposed to the earth of humans. Dragons, being air and fire, are better but not common (being a familiar is beneath most dragons' dignity). Nowadays most wizards scorn the use of familiars and instead use other methods, often runes written on their skin, to channel power to their aetheric inside. These methods are not as good, since they don't allow for dynamic altering of the flow (very important in some tightly timed and intricate spells) and don't offer a very wide channel, but are easier and neater than a familiar.
It is possible - but unusual - to develop more than one channel, to allow one to operate many channels at once and thus gain more magic. This is difficult and needs long, intensive training and a strong mind.
Magic requires power and power comes from conflict. A common conflict is elemental, so fire/water and earth/air are good power-generators. Because of the chemicals sloshing around inside them, most organic beings have a certain level of power, but in general, not very much (fae are the exception; their power level is high and they disdain to use any magic save that which originates within themselves; as a result, their magic is high-precision and elegant but not as powerful as the truly great channellers of other races). Women almost always have more innate power because they have a greater internal variability. More power can be gained by stimulation of body processes - cutting, sex, etc.
External power is often generated simply by calling on the energy around one. For a spell which may require a lot of energy, conditions can be set up to deliver power - a common method of generating power is to float lit candles on water. Although they do not touch, the opposing elements generate enough power from their proximity for most spells. It is considered courteous to set up one's power source this way rather than to draw indiscriminately from around oneself.
A spellcaster controls the flow of aether with his/her/its mind. For most beings, patterns are very useful, so, for example, a spell can be spoken, sung, drawn or danced. The more a pattern is used, the better an individual will become at casting it, because his mind becomes used to guiding the aether flow through the pattern. Common spells like the come-back spell are almost ingrained from childhood. One spell that is so old even non-mages can use it (given access to some form of power), is the general exorcism spell. It has been used for millennia, is highly ritualistic and makes heavy use of alternative channels, and the innards of the spell (the pathways and force flows) are set up outside the exorcist using the ritual.
Computer wizardry is an art akin to the magic of the fae - it is both subtle and powerful, manipulating dimensions and conditions in such a small way that it is unlikely to require more power than the mage holds within themself. Yozhik is very skilled at manipulation and is a more-than-adequate channeller.
Biowizardry is more concerned with finding out about biological magic and things using magic. Much of the science is carried out using machines, but biowizards still need to be able to use magic. Hence Meg's remark 'some is theory, some is machines, and the rest doesn't work.'
Theology is more concerned with the theory of the spiritual beings. Many theologians are magic users, many are not. Only magic users, however, can draw circles.
The Tiger's Eye gating means the mage has variable channels. They are almost all caused by damage of some kind; Meg's from the fire at her village early in her life. It's not a desirable state to be in. Meg's attempts to use runes fail miserably because her channels vary from Ivory to Iolite, and the runes can't offer a wider channel than Amber. If her gate is wider than that, the aether flow will flood through her natural gate and not her runes and will not be controlled. She doesn't understand a lot of the theory anyway, so what control she has is not particularly great.
(Vitenka) Innnteresting. I assume that the FireBird?'s channel was larger than all of her natural ones?
Phoenixes are inherently magical. I'm not sure the concept of channelling applies to Daedalus. If they were less rare and/or dangerous, they'd be in high demand as familiars.. - SunKitten