The game system is rather innovative, with everything based on d10. The core of the system (not surprisingly) is the magic system: one or more of five actions (create, command, perceive, change, destroy) are combined with multiple objects (fire, water, air, earth, plant, mind, images, animals, magic force....) to achieve countless effects. Magi have a limited number of spells they learn, but can innovate and create new effects on the spur of the moments (although of course with less ease). For the first time, magic is treated in a game as a serious object of study: magi are supposed to spend a long time in their laboratories, preparing new spells and potions, and increasing their knowledge of the hermetic arts. The other main innovation was the insistence on play-acting the characters - indeed, many characteristics of the later Storyteller system developed by White Wolf Games can be traced to Ars Magica (and the fact that both Ars Magica and the Storyteller system were both developed by the same person)
Ars Magica is an example of a Troupe System, although a number of Campaigns (known as Sagas) will have most stories run by the same person, known as the Alpha Story Guide.
Originally developed by Jonathan Tweet and Mark Rein-Hagen in the late 1980s, Ars Magica was first published by Lion Rampant games. In the early 1990s, rights to Ars Magica were acquired by White Wolf Games, the company Rein-Hagen had in the meantime founded. White Wolf Games published the Third edition, which greatly expanded the settings and peripheral rules while leaving the core system intact. White Wolf also published many supplements, detailing specific regions of Europe, or outlining stories that could be played in the original setting. Ars Magica was later sold to Atlas Games, who revamped it with a fourth edition and has published new source-books since. The fifth edition is currently in early playtest stages, and is tentatively scheduled for a late 2004 release.