Catholic Church
The Catholic Church was the main body of followers of Christianity.
To enforce their religion, the Church kept many books which they deemed heretical in the secret Library of St John the Beheaded in London. (NA: All-Consuming Fire) One of the books suppressed by the Church was the Necronomicon. (EDA: The Banquo Legacy)
In the 16th century, many Christians split from the Catholic Church to become Protestants. Many faithful Catholics persecuted them, such as Mary I of England with the Heresy Laws, and Catherine de Medici of France with the St. Bartholomew's Day Massacre. (BFA: The Marian Conspiracy, DW: The Massacre of St Bartholomew's Eve)
In 1609, Cardinal Robert Bellarmine of the Catholic Church moderated the Armageddon Convention. (MA: The Empire of Glass)
In 1940s Croatia, Catholic partisans captured, shot, and buried the vampire Yarven. (MA: Goth Opera)
In the 26th century, Claire Summerfield, the mother of Bernice Summerfield, was Catholic. (NA: Love and War)
By the 28th century, the Catholic Church had re-established itself and become a major space power with jurisdiction over numerous worlds. (TN: Companion Piece)