The Ars Magica sourcebook for the Dominion. Since I wrote it, I prefer to tell you what it's not. It's not a handbook for the medieval church: that information will be in the Medieval Handbook (appropriately). It's not a study of the metaphysics of Christianity. It's a practically-oriented guide for Storyguides who would like to include the Dominion in their stories in a more direct fashion. Included are rules for clergy, a new trait called Piety (the counterpart to Hierarchy if you will), and such things as Angels and Pious Magi. Also is a Saga outline called Cestus Dei, which brings the Order of Hermes into direct conflict with the Church over an object sacred to both: the Holy Grail.