First published in 1987, Ars Magica is a tabletop RPG set in a version of medieval Europe where magic is real and all the player-characters are wizards. Well, technically. One of the novel ideas of Ars Magica was "troupe-style play" in which every player created multiple characters, playing different ones as the story dictated. You might be a powerful wizard of the Order of Hermes one week, then one of their menial sidekicks called "grogs" the next.
Ars Magica also pioneered rules for shared worldbuilding, with players collaborating to create a covenant—a stronghold where the wizards and their associated outcasts and misfits banded together. It also suggested players take turns being the Game Master or Story Guide, each telling different stories in Mythic Europe before handing on the reins.
Another area where Ars Magica innovated was its magic system, as you'd expect for a game so heavily focused on wizards. As well as pre-made formulaic spells, magicians can invent spontaneous ones on the fly by combining a technique and a form—a verb and a noun, each with a Latin name. To make fire, for instance, you combine the technique of creation Creo and the form of fire Ignem, which gives you something snappy to say when a fireball goes off.
The fifth edition of Ars Magica was released in 2004, and its last supplement came out in 2016. Publisher Atlas Games has announced it's been working on a Definitive Edition for the last few years, a revised version of fifth edition it's planning to crowdfund in fall, 2024. "We'll release a deluxe, full color, hardcover print edition of the Definitive core rulebook," Atlas said, "with new art and layout and heirloom production quality."
It'll be "much bigger" than the 5th edition book, with revisions that "reflect decades of play and incorporate a host of new material published since the original rulebook's release." It'll also be based on an open license.
"We recently completed our long-term project of resurrecting original printer files for the entire Ars Magica 5th Edition line of supplements," Atlas said, "converting them to softcover print-on-demand. This means that the entire line of supplements, fully compatible with ArM5D, can remain in print indefinitely, both as ebooks and as printed books made to order and delivered to buyers anywhere in the world. We intend for Ars Magica to be a game enjoyed and creatively expanded for generations to come."
Ars Magica will be familiar to fans of the World of Darkness games. Its rules became the basis for the WoD's storyteller system, and parts of its background inspired similar concepts in games like Vampire: The Masquerade (in Ars Magica, the Tremere haven't yet turned undead and are simply dark wizards) and Mage: The Ascension (which is essentially Ars Magica in the modern day).
There was an attempt to crowdfund a videogame based on Ars Magica in 2012 by Black Chicken Studios, but unfortunately it fell short of its goal.