From Satan Service
Whether the brainchild of those originating and driving subversion ideologies, or the innovation of those who genuinely hated and sought to ridicule Christian religion, the Black Mass has arisen clearly as a travesty of Christian rites, particularly the Roman Catholic Latin Mass, which was liturgical convention until the mid-20th century, when the Vatican II reform forced a move toward regional languages.
With the invention of religious Satanism in the late 1960s, and particularly with the publishing of The Satanic Bible, the expansion of this notion to trans-religious character made its debut. In it, Anton LaVey made plain his intention that the Black Mass serve as a deconditioning tool en par with anti-brainwash techniques of the late 20th century, focussing entirely on the religious tradition from which the participants have come and seek to escape. The inversion and mockery of the symbolism of their entanglement would be used to retrain their psyches in pursuit of personal liberation.