From the publisher website:
World of Mystery; World of Myth
Your covenant is one of power and authority, control and mastery. To reach this pinnacle you have seized the lands around you, dominating all their meek inhabitants. You are lord of all you survey. However, there is a much greater world beyond the not-so-far horizon, a world controlled by others beyond your so-called power, a world waiting to put you under its heel. That world is Mythic Europe, and you are but a spark of light before its ominous shadow.
Mythic Europe is a story supplement that presents the official setting of the Ars Magica game. It provides extensive and precise detail about the harsh medieval realms of your bold saga. It is of value to players and storyguides alike.