O.T.O. also encompasses Ecclesia Gnostica Catholica (E.G.C.), the Gnostic Catholic Church, which was originally brought into the Order by Theodor Reuss through Dr. Gérard Encausse (Papus) in 1908 e.v. The E.G.C. is an explicitly religious Thelemic environment, dedicated to the advancement of Light, Life, Love, and Liberty through the Law of Thelema.
The central activity of the E.G.C. is the celebration of the Gnostic Mass, Liber XV, which was composed by Aleister Crowley for O.T.O. in 1913 e.v. Members of O.T.O. in good standing are eligible for clerical training and ordination in E.G.C. Many O.T.O. local bodies celebrate the Gnostic Mass on a regular basis. In many locations, no formal affiliation with O.T.O. is required to attend Mass, although visitors are expected to communicate the sacrament.
The E.G.C. Clergy is composed of the Father or Mother of the Church, the Primates or Presiding Bishops, the Bishops, the Priests and/or Priestesses, and of the Deacons. The Lay Membership consists of persons who have undergone the ceremonies of baptism and confirmation.
The public ceremony of baptism may be administered by any Priest or Priestess of E.G.C. under the direct or indirect supervision of a Bishop or Auxiliary Bishop. The person baptized must be of at least 18 years of age, and need not be an Initiate member of O.T.O. Baptism does not confer Lay Membership in E.G.C.
The public ceremony of confirmation may be administered by any Priest or Priestess of E.G.C. under the direct or indirect supervision of a Bishop or Auxiliary Bishop. The person confirmed must have previously been baptized, must have committed the Creed to memory, and show evidence of commitment to E.G.C. Two sponsors are required. Confirmation confers Lay Membership in E.G.C.
Ordination to the Diaconate in E.G.C. may be performed by any Bishop or Auxiliary Bishop of E.G.C.; or in the absence of a Bishop or Auxiliary Bishop, by any Priest or Priestess of E.G.C. under the direct or indirect supervision of a Bishop or Auxiliary Bishop.
Recognition of sacerdotal authority within E.G.C. All persons who attain to the degree of Knight/Dame of East and West of O.T.O. are, as part of their initiation, ordained as priests/priestesses of E.G.C.
A ceremony conveying recognition of sacerdotal authority within E.G.C. may be performed by any Bishop or Auxiliary Bishop of E.G.C.
The term ‘Bishop’ as used herein shall mean a Bishop who possesses the Theoreticus sub-degree of VIIº unless the term is preceded by the word ‘Auxiliary’ or followed by the words ‘in Amity’.
The Outer Head of the O.T.O. is ipso facto the Sovereign Patriarch or Sovereign Matriarch of E.G.C. At this time, Frater Superior of the O.T.O., Hymenaeus Beta, is the Patriarch of the Church, known under his ecclesiastical name as Tau Silenus.