In 1308 Pope Gregory IX enlists the Dominicans to root out and destroy a sect know as the Cathars which renounce all the rituals of the Catholicism in favor of simple spiritualism. This simple faith had great appeal to illiterate villagers who had little understanding of the Roman Catholic Church they belonged to. Thus begins the Inquisition.
Seeing the Roman Catholic Church threatened by the Protestant Reformation Pope Paul IV unleashes the Roman Inquisition especially directed at the publishing houses in Venice that are distributing proscribed books containing heretical dogma.
In his conquest of Europe Napoleon encounters and abolishes the Inquisition and its ongoing atrocities in France, Spain and northern Italy. But with Napoleon's fall from power the Inquisition returns with vengeance. Despite causing substantial public relations damage to the Catholic Church in the modern era it is not substantially curtained until the Church is conquered by the newly unified nation of Italy.