Borja has obtained a copy of a legendary book, "Of the Nine Doors of the Kingdom of Shadows", whose author was burned at the stake by the Inquisition. The book purportedly contains instructions for summoning the Devil. Only one copy of the book is supposed to have survived, but Borja claims three exist, two of which are elaborate forgeries. He hires Corso to compare the three copies and obtain the legitimate one by any means necessary. He promises to pay handsomely and cover all expenses.