Spheres are areas of spellcasting - all magi belong to one or other of them. The seven spheres are listed below. A magi's power is trained to one of them, or in some very rare case to more than one, and to the god that governs the sphere.
The seven spheres are:
Fire
Water
Earth
Air
Spirit
Heavens
Death
The spheres affect the way a magi affects, and behaves. For instance, magi of the Fire sphere tend to have volatile personalities, ready to flare up at any imagined insult or slight towards their family, race, religion or so on. To the opposite end, magi of the Water sphere have a larger tendancy to be calmer, and let people deal with matters. However, they also have reputations as cunning manipulators. Bear in mind that these are stereotypes, and do not represent all the magi of a sphere.
It seems fairly obvious, then, that spheres have their opposites. Fire is Water's opposite, Earth is the opposing force to Air, and Death is Heavens' antithesis. Magic of these spheres are usually least effective against its opposite, as both can cancel each other out.
The exception is Spirit, which has no opposite. Spirit magics exist everywhere and nowhere, where you most expect and perhaps where you would least count on. Their wizards use spells that are different to other spheres' spells - instead of brute force or even defensive magics, Spirit spells are normally invisible to the human eye. They can turn a warrior against his will, inspire a thought where there was none at all, use telekinesis, and many other abilities. For this reason Spirit sphere magi are sometimes expelled from any establishments when found, for fear that some innermost secret may be discovered. So Spirit magi can make useful spies.
The power of certain spheres can wax and wane, depending on the terrain and natural environment of the surroundings. For instance, Water magi are supreme in a boat, and they can produce spells that can influence weather, calming storms and soothing rough seas. Earth sphere magi are most powerful upon land, but their powers are next to useless when flying. Fire have no particular domain of power, but it has been noticed that they are more powerful weapons-users than any other sphere except perhaps for Death. They are weaker in water.
Those are the four elemental spheres. The other three, Spirit, Heavens and Death, rely on consecrated areas to make their spells more effective. A magi, cleric or sorcerer can consecrate an area, although it comes much more naturally for a cleric. Again, a cleric must worship the god who governs the sphere a magi bows to for this to work.
Finally, Death sphere magi are much to be feared. They are agents of the dark god Nagharos, overlord over the realms of the dead, but also Ar'Gerin, lesser god of whisperers and deceit. They can be most effective with their daggers, curved and poisoned, so that they may better carry out the commandments of their gods.
