The Book of Magic: the Basic Idea
What exactly is magic?
In game terms, we define magic as the manipulation of probability to achieve effects that would be impossible under normal circumstances (or, at the very least, incredibly unlikely). A body that can alter probability in order to manifest magic is often known as a mage, magician, wizard, thaumaturge, or sorcerer. Lots of colorful names to be sure, but all of them are essentially the same thing: people that use magic.
Through long and intense studies, almost anyone can learn how to use magic. Sure, some people have more... potential than others, but this matters not. When it comes down to it, any sentient being can master magical practices if he wants to. This is because, more than sleepless nights studying and researches into the crypts of long dead enchanters, the desire to master the arts arcane is what it truly takes to become a wielder of magic.
At a glance, a spellbinder looks to be a relatively frail form of ascendant being. His or her physical abilities will be comparable to their 'mundane' counterparts, and in fact there is little to distinguish a conjurer from ordinary society, once you remove the familiar trappings of robes, amulets and so forth. There is no genetic marker to reveal wizardry, nor is there obvious, permanent physical cues to showcase such.
But a theurgist's seeming weakness belies his true power. Using knowledge of the obscure as their power base, all magic-using entities can wield staggering power, the ability to reshape reality itself to suit their desires. And their desires are paramount, for logic need not hamper a warlock in the course of his work - merely the will to impose his wishes on the world at large... no matter how far removed from reality they may be.
Core Principles
Before you build your very own magic wielding player character for use in the game, there are several basic ideas that one should understand first.
Spells
The principal thing to remember about magical spells is that they are not powers, in the standard sense of the word. They are instead like talents, as they are arcane formulae that a person can use to manifest magic. As such, standard methods of power negation do not work on practitioners of magic, as their powers are derived from what they know, not some inherent effect of their physiology.
These arcane formulas are known as spells. As opposed to the dangerous means necessary for ordinary heroes to acquire powers, a mage can learn a new spell with only a bit of studying and hard work. Research, also, is a large part of spell acquisition. Further, spells all affect reality in the same way, regardless of the various types of raw energy they use to fuel their effect.
You see, magic is the art of making the impossible possible. By tinkering ever so slightly with the laws of probability, practitioners of magic cause things to happen which simply should not occur - at least, not according to our current understanding of the universe. Those strange words, the bizarre movements, and even the occult ingredients, they are all tools for the bending of reality itself to the whims of the mage.
Types of Magical Energy
In essence, there are three kinds of magical energy: personal, universal, and dimensional energy. Each mage has access to all three types of magical power, generally speaking, but players can limit their mage's access to energy types as a character limitation (see character generation, later, for more on this). The forms of magical energy function as follows:
Personal Energy: derived from the spell caster, personal energies can fuel spell effects without relying upon any outside sources whatsoever. While magic of this type is more exhausting for a mage to utilize, it is not at all hindered by the whims and dictates of outside agencies or beings. Personal energies are used primarily to affect a caster's own body or equipment, as opposed to affecting others or the outside world.
Universal Energy: this form of magical energy is drawn from the ambient and infinite power of the universe itself. The power inherent in universal energy can be used to affect people and things other than the mage himself, and is the power source of most of your more legendary spell effects, such as bolts of energy, matter transformations, and the like. Universal energy magic is less stressful to use than personal energies.
Dimensional Energy: this last form of magical energy is extremely potent, as it is drawn from outside a spell caster's own plane of existence. Spells that use dimensional energy are the least stressful on a mage, as the power that fuels them does not subtract from his own energies at all. However, energy of this type is often granted to a mage by some being or race of great power, which is a risky idea, at best.
Unless, of course, you like the idea of a vengeful god taking notice of you.
Types of Magical Spells
In addition to there being several types of magical energies, there are several special types of magical spells that use them. It's true that some magic spells can be defined as just 'personal', 'universal' or 'dimensional' spells, but others don't easily fit into this mold. These special types of spells include school spells, group spells, and entreaty spells, each of which is detailed here:
School Spells: these are special magic spells that are usually, but not always, unique to one magical school of study (see magic schools for more on these). They can be of any type of magical energy, of course, but only the mages who study a magic school will have access to its particular school spells. This 'exclusive' availability is primarily due to the mindset involved in creating such magics in the first place.
Group Spells: normally of dimensional energy, a group spell is in fact several spells, as it acts as a kind of multiple choice ability. It is actually five or six different spells, of similar type, and a mage can choose one to use each day. He need not make this choice until he actually needs to cast the group spell, though - this makes them more versatile and more limited at the same time.
Entreaty Spells: these spells have the greatest potential power, as well as the greatest inherent risk. Dimensional energy effects also, these spells are an attempt to draw power from a specific entity, item, or plane. Planes and items usually don't cause too much trouble, but power requests from gods tend to get a mage into trouble, as the gods eventually ask for favors in return.