The core rules of the game are similar to those in other World of Darkness games; see Storyteller System for an explanation.
Like other storytelling games Mage emphasizes personal creativity and that ultimately the game's powers and traits should be used to tell a satisfying story. One of Mage's highlights is its system for describing magic, based on spheres, a relatively open-ended 'toolkit' approach to using game mechanics to define the bounds of a given character's magical ability. Different Mages will have differing aptitudes for spheres, and player-characters' magical expertise is described by allocation of points in the spheres.
Deals with spatial relations, giving the Mage power over space and distances. Correspondence magic allows powers such as teleportation, seeing into distant areas, and at higher levels the Mage may also co-locate herself or even stack different spaces within each other. Correspondence can be combined with almost any other sphere to create effects that span distances.
This sphere gives the Mage power over order, chaos, fate and fortune. A mage can sense where elements of chance influence the world and manipulate them to some degree. At simple levels machines can be made to fail, plans to go off without a hitch, and games of chance heavily influenced. Advanced mages can craft self-propagating memes or curse entire family lines with blights. The only requirement of the Entropy sphere is that all interventions work within the general flow of natural entropy.
Forces concerns energies and natural forces and their negative opposites (i.e. light and shadow can both be manipulated independently with this Sphere). Essentially, anything in the material world that can be seen or felt but is not material can be controlled: electricity, gravity, magnetism, friction, heat, motion, fire, etc. At low levels the mage can control forces on a small scale, changing their direction, converting one energy into another. At high levels, storms and explosions can be conjured. Obviously, this Sphere tends to do the most damage and be the most flashy and vulgar. Along with Life and Matter, Forces is one of the three 'Pattern Spheres' which together are able to mold all aspects of the physical world.
Life deals with understanding and influencing biological systems. Generally speaking, any material object with mostly living cells falls under the influence of this sphere. Thus, being alive protects a thing from direct manipulation by the Matter sphere and vice versa. Simply, this allows the mage to heal herself or transform simple life-forms at lower levels, working up to healing others and controlling more complex life at higher levels. Usually, seeking to improve a complex life-form beyond natural limits causes the condition of pattern bleeding: the affected life form begins to wither and die over time. Along with Matter and Forces, Life is one of the three Pattern Spheres.
Matter deals with all inanimate material. Stone, dead wood, water, gold, and the corpses of once living things are only the beginning. With this Sphere, matter can be reshaped mentally, transmuted into another substance, or given altered properties. Along with Life and Forces, Matter is one of the three Pattern Spheres.
Dealing with control over one's own mind, the reading and influencing of other minds, and a variety of subtler applications such as Astral Projection and psychometry. At high levels, Mages can create new complete minds or completely rework existing ones.
This sphere deals directly with Quintessence, the raw material of the tapestry, which is the metaphysical structure of reality. This sphere allows Quintessence to be channeled and/or funneled in any way at higher levels, and it is necessary if the mage ever wants to conjure something out of thin air (as opposed to transforming one pattern into another). Uses of Prime include general magic senses, counter-magic, and making magical effects permanent.
This sphere is an eclectic mixture of abilities relating to dealings with the spirit world or Umbra. It includes stepping into the Near Umbra right up to traveling through outer space, contacting and controlling spirits, communing with your own or others' avatars, returning a Mage into a sleeper, returning ghosts to life, creating magical fetish items, and so forth. Unlike other Spheres, the difficulty of Spirit magic is often a factor of the Gauntlet, making these spells harder for the most part. The Sphere is referred to as Dimensional Science by the Technocratic Union.
This sphere deals with dilating, slowing, stopping or traveling through time. Due to game mechanics, it is simpler to travel forward in time than backwards. Time can be used to install delays into spells, view the past or future, and even pull people and objects out of linear progression. Time magic offers one means to speed up a character to get multiple actions in a combat round, a much coveted power in turn-based role-playing.
One of the plot hooks that the second edition books put forth were persistent rumors of a "tenth sphere". Though there were hints, it was deliberately left vague. The final book in the line, "Ascension" implies that the tenth sphere is the sphere of Ascension (in as much as spheres are practically relevant at that point in the story). As the book presents alternative resolutions for the mage line, Chapter Two also presents an alternative interpretation that the tenth sphere is "Judgement" or "Telos" and that Anthelios (the red star in the World of Darkness metaplot) is its planet (each sphere has an associated planet and umbral realm).
The various sphere sigils are, in whole or in part, symbols taken from alchemical texts.