St. Pius V’s reforms of the Roman Catholic Church in the 16th century included restricting the use of indulgences and dispensations from holy vows and reforming the entire system of penance. He also condemned nepotism and sharpened the rules governing the Inquisition to root out Protestantism in Italy. Many old charges of heresy, long suspended, were revived, and rank offered no protection to those suspected of being heretics. His papacy also established the Index Librorum Prohibitorum, a list of books condemned as dangers to faith and morals.
Pius’s additional reforms included fixing penalties for Sunday desecration, profanity, and animal baiting; compelling members of convents to live in strict seclusion according to their vows; ordering instruction in the catechism (a manual outlining the principles of Catholicism); and issuing an improved breviary (the daily prayers for clergy and nuns) and missal (a book containing the prayers and responses for celebrating the mass).