Living Lore

From the publisher website:

In Mythic Europe, kings rule their feudal lands, but their wives can be stolen by magic. The church preaches repentance, and saints manifest on Earth to enforce their will. Countries can be changed into lakes, and whole islands hidden from all who are unworthy to find them. A cat can be a guardian of great power, and a leopard the agent of divine justice. The dead might return to further serve their infernal masters, or be led across the continent in Hellequin's Hunt.

Living Lore is a hardcover supplement for Ars Magica, containing dozens of medieval legends adapted for your saga. Whether you want a tempting faerie or a new mystery cult, there is something for you in this book.