Malleus Maleficarum

Harry Potter gets swept up from his relatives' door by two emissaries of the Magical Vatican, much to Dumbledore's dismay. Years later, right at the beginning of the Second Voldemort War, Dumbledore menages to convince the Vatican to make him return in Britain and attend Hogwarts. Unfortunately for the old wizard, Young Harry isn't what he expected him to be (VERY SLOW UPDATES)