This section is a little more intertwined in the RPG aspects of working magic in this world, i.e. game mechanics, rules, etc. I’m open to new ideas but this was sort of a system I devised:
Mages
Mages are limited by several factors when wanting to cast a spell:
*they must have an inherent magic ability (magery). This is fairly common, though sometimes not developed
*they must study in a college of magic to a fairly high level of proficiency (fire, mind control, plants, etc.)
*they must have a scroll created by an alchemist for each casting (hence alchemists and their products are highly valued and respected)
*Spheres appear at random in the world, some stay for longer than others (entire cities are built around strong, permanent ones). Typically the more powerful the more permanent. Each sphere is tied to a college, often linked to the environment. A water sphere near a river may allow spells to be cast that can manipulate water.
*an incantation, a scroll, a sphere, and a focused image of what they want, and the spell is cast.
Thus, a mage who has studied fire and has an appropriate scroll and is near a fire sphere can form/shape fire in any way he wishes, though some take more skill and stamina: a small campfire, a series of fireballs, a fire elemental.
Alchemists
Alchemists study their craft carefully for many years. The best can charge quite highly for their product. More shady, fly-by-night alchemists may provide cheap, quick product, but it may be very unreliable.
Alchemists themselves don’t have much power, but are generally safe from robbery and such. Sure, their current supply of scrolls may power a mage, but the alchemist would refuse to produce any more for the mage after such a theft. For anyone considering a quick buck, many alchemists have close relationships with one or more mages whom they can call upon for a quick favor when they need to (i.e. killing a thief).
Spheres
The spheres are a great unbalancer in magic. Spells can be cast without them, though at great cost to the caster. Power struggles between cities and nations may erupt over newly discovered spheres.
Law
Generally beneficial magery is allowed, harmful magery is treated like any other attack. Mages form guilds, and aid the law in rounding up malovelent wizards. In some societies, magery is forbidden.