So the Book of Vile Darkness has some cool rules that cover possession. But I'd like some rules for exorcism. Anyone seen any or house ruled them before?
The best rules I have seen for Exorcism is in the Demon Hunter's Handbook on pages 34-38 published by Goodman Games and reiterated in The Quintessential Cleric II - Advanced Tactics Book Three on pages 85-89. Very complete, in depth rules for how to Game Master an Exorcism, including in-game time, resources, skills and checks, and modifiers to successfully do so. These advanced rules are NOT simply, cast this spell and the possessing demon is forced out of the victim. These rules simulate an actual in-game Exorcism encounter that resembles the classic exorcism as seen in the movie The Exorcist. It simulates the resistance of the possessing demon and the toll on both the victim and the exorcist, representing the back and forth power struggles between the forces of good and evil. If you want to make the Exorcism a major plot point or even make the Exorcism an entire encounter for the adventure, then these are rules for you. If you just want to get the possessed demons out of your PCs and move on with your story, then use the spells as outlined by our peers.So the Book of Vile Darkness has some cool rules that cover possession. But I'd like some rules for exorcism. Anyone seen any or house ruled them before?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.