From the back of the book:
Price of Power
From their unfathomable domains, the powers beyond life call forth your soul. Your burdensome choice lies between Light or Dark, and your fate hangs in the balance, either for torment in life and paradise beyond, or paradise in life and torment beyond. Choose Dark and all the world is your bauble, its every craven satisfaction yours to relish. You are master over all, magical or mundane. And what is the price for this glory? Merely your paltry, intangible soul. Yet, why does the shadow grin?
Price of Soul
The Maleficium is an Ars Magica Third Edition sourcebook that explores the machinations and mystique of the Infernal Realm. With this reference Storyguides and players may pierce netherworldly deceptions and secrets, bringing about confrontations with the Evil, and mastery of the Dark Arts. You may now become a Magus opposed to the Light and the Order of Hermes itself.