Just some general notes on magic. Will make them more coherent later.
Magic is everpresent, but controllable
magic is a rarity. One must be born with a sensitivity to magic and usually a talent for shaping it.
Controlling magic is an exhausting activity. Those who control magic are called mages or magicians. Wizards and witches are those with no inborn magical ability who learn to control magic.
Magic works much better when it is allowed to act on it's own will. Those who simply act as a conduit for magic are called wilderlings. Wilderling magic is unpredictable and chaotic, and the caster may not even realize they channel magic.
If a magician channels too much magical energy into a controlled spell, they risk magical burn-out or death (or possibly both). Wilderlings also risk burnout, but the risk is much lower for them. Burn-out means that the person in question can no longer channel magical energy.
Magic runs in a natural network of ley lines. The ley lines run everywhere, and can be at any spot on the earth or above or below it. The closer one is to a ley line, the more raw power they have access to. Wilderling magic tends to be much more spectacular the closer one is to a ley line. The risk of burnout is also much greater the closer you get.
Magic users are generally rare, and as such, can either mass great political power, or will be hunted, depending on race and location. All wilderlings have the capability of learning to become magicians if they recognize their power and choose to. However, this does not mean that one has to be a wilderling in order to become a magician or wizard.
Controlled magic obeys the Laws of Magic. (Law of Association, Law of Balance, Law of Contagion, Law of Finite Senses, Law of Identification, etc. See The Mystica: Laws of Magic
for information about the laws of magic.)
Alchemy is not the same thing as magic, although it may operate on some of the same principles. Alchemy is primitive chemistry.
It is very rare for a magician or a wizard to become very powerful, because most are either killed or experience burn out before long. Every time a magician or a wizard tries to control magic in order to shape a spell, there is a chance the power will be too much. This varies directly with the amount of power called and the complexity of the spell. If there is too much power, one of four things happens: the magic user loses control of the spell (a wild surge); the magic user maintains control of the spell, but is burned out; the magic user loses control of the spell and is burned out; the magic user is killed.
Wilderlings face similar dangers. They can call on magic, but cannot specify the effect. Generally, the effect will favor the caster, however. A wilderling can also attempt to specify an effect, but then face a severer risk than magicians, due to a lack of training. Sometimes, magic will be channeled without the conscious knowledge of the wilderling. In this case, the risk of death or burn-out is lessened. In the case of too much power being channeled, wilderlings only face death or burnout, since they generally don't try to control magic.
Generally, the more conscious effort is made to control magic, the greater the risk that something bad will happen. This is further affected by training, race (some races have a greater inborn affinity for magic), proximity to ley lines, and other factors.
In populated areas, the ley lines are fairly well mapped, but they do change.