Black Magic is Not a Myth in Articles by Aleister Crowley.
“The ‘Black Mass’ is a totally different matter.
I could not celebrate it if I wanted to, for I am not a consecrated priest of the Christian Church.
The celebrant must be a priest, for the whole idea of the practice is to profane the Sacrament of the Eucharist. Therefore you must believe in the truth of the cult and the efficacy of its ritual.” [via, also]