High Quality Content by WIKIPEDIA articles! Ecclesia Gnostica Catholica ( E.G.C.), or the Gnostic Catholic Church, is the ecclesiastical arm of Ordo Templi Orientis (O.T.O.), an international fraternal initiatory organization devoted to promulgating the Law of Thelema.Thelema is a philosophical, mystical and religious system elaborated by Aleister Crowley, and based on The Book of the Law. The word Catholic denotes the universality of doctrine and not a Christian or Roman Catholic belief set.