This is the best magic system in any RPG that I have come across. Magi learn magical Arts, of which there are fifteen. Five are Techniques, creating, for example, while the other ten are Forms, such as mind and fire. The magus's ability to cast a spell is calculated by adding together the appropriate Technique and Form. Magi can cast formulaic spells, which have defined effects, or spontaneous magic, which does whatever the magus wants, if he is powerful enough.
Spontaneous magic is much more flexible than formulaic, but also weaker.
The game provides detailed guidelines for what can be done with the various Technique and Form combinations at different levels of power, so that it is fairly easy for the Storyguide to adjudicate the effect of a spontaneous spell. The magic system also provides extensive rules for magical study and research. Magi can improve their Arts, invent new spells, create magical items, train apprentices, and bind familiars. Mythic Europe Mythic Europe is the official setting of Ars Magica. The power of the divine protects its own, but magi are generally outside its influence.