The act of segregating, discriminating or mass murdering large groups of people due to religious differences. Often thought as purification, it is an ancient practice used to "cleanse the world" of anyone who is not a member of that particular religion. Anyone opposing the purification are imprisoned, expelled or slaughtered in the name of whatever god or diety posessed them to commit the atrocity.
Caleb: Whatever happened to the religious order that used to that religious bunch in the next town?
Dave: I heard they were rounded up and either taken away or executed. Something about a religious cleansing.