From the publisher website:
Fifty years ago, the covenant of Calebais was destroyed.
No one knows how or why such a powerful and well-defended group of wizards could possibly fall. The truth behind the tragedy only comes to light when you and your friends uncover this mystery. From faerie-inhabited forests to the long-abandoned ruins of a wizardly palace to the inner chambers of a secretive convent, The Broken Covenant of Calebais goes to the roots of roleplaying -- to the early days of fantasy stories -- when realism, romance, mystery, and magic were foremost in mind.
This revised edition of The Broken Covenant of Calebais is the third version of the adventure to be published for Ars Magica. Calebais was the first adventure published for the First Edition of the game, and was reworked for Second Edition. Now, to coincide with the release of the game's Fifth Edition, this classic has been revised and expanded once more. Although the plot, setting, and atmosphere remain the same, the text has been almost completely rewritten to integrate this classic adventure into the newest and best version of Ars Magica.