The medieval Church established its monopoly over the spiritual life of Europeans in the Early Middle Ages (c. 476-1000) and consolidated that power throughout the High Middle Ages (1000-1300) and Late Middle Ages (1300-1500). Along the way, the clergy became increasingly corrupt, ignored basic tenets of Christianity, and often lived lavishly on the tithes of the people.
This is a companion discussion topic for the original content at https://www.worldhistory.org/article/1414/six-great-heresies-of-the-middle-ages/.