The notorious black mass was supposedly a blasphemous parody of the Catholic mass celebrated by witches or sorcerers for the purpose of defiling the most holy beliefs and practices of the Church, and thereby pleasing the Devil, who would as a reward grant to them the power to do evil.

Some of its infamous features include a defrocked priest who celebrated the mass on the belly of a naked woman, and the substitution of semen for the holy chrism oil, urine for the wine, and blackened turnip or excrement for the host. During the course of the mass, the defrocked priest was said to copulate with the woman serving as the altar. Sometimes the priest inserted holy wafers into the vagina of the woman before copulation. Sometimes the copulation was anal. The words of the ritual were read backwards or distorted by replacing "God" with "Devil" or "Satan." The sign of the cross was made backwards. One entertaining account claims that the mass was celebrated by a talking goat who read from a missal bound in wolf's skin.

The general principle of the black mass is that the mass of the Church should be inverted. Whereas the regular mass is intended to do good, the black mass was celebrated to do evil. For example, in the court of the French king Louis XIV, black mortuary masses were performed by selected priests for the purpose of causing the deaths of specific individuals. Occasionally amatory masses were performed by priests to enable them to magically overcome the modesty of nuns they lusted after.

One such amatory mass was described by an observer in these terms:

Every time during the course of the mass when the priest had to kiss the altar, instead he kissed the body of the girl. He consecrated the host over her private parts, into which he inserted a small portion of the host. At last the mass was finished, and the priest went into the woman, and, with his hands dipped into the chalice, washed all her genital areas.

Even more fantastic details of the black mass involved the sacrifice of infants or maidens, and a general orgy among the participants during which ties of marriage and family were completely disregarded. The best accounts of this sort of ultimate depravity are to be read in the Marquis de Sade's novel Justine and in the nineteenth century French writer Joris-Karl Huysmans' novel La Bas.

There is a general consensus among those who have researched the subject that the black mass is largely a literary fiction, and was never practiced by groups of witches (if groups of witches ever even existed). Witches were accused during the witch trials by the Inquisition of defiling the instruments and rituals of the Church, but these accusations have very little merit. They appear to have been largely the perverted fantasies of the monks and priests who supervised the interrogations. Tortured beyond endurance, it is no wonder that the accused women often admitted to these charges merely to bring about a temporary halt to their agony.

The term "black mass" was first used in English in 1896. There is little evidence that a true black mass was ever celebrated earlier than the late 17th century. Prior to this period, sorcerers occasionally used the ritual forms of the Church for their own purposes, to accomplish desired goals by their magic. When the purposes were evil, the ritual practices sometimes involved the perversion and defilement of Catholic religious practices. However, the black mass as a celebration or homage to Satan or the Antichrist is a relatively modern activity. It was performed in the French royal court, and probably in England by members of the Hell-Fire Club. Possibly it was also done in the Russian royal court. It is unlikely that black masses were ever used in the rituals of the Knights Templar, even though the Knights were accused of trampling and spitting on the cross.

Black masses formed a part of the religious practices of the late Anton Szandor LaVey and his Los Angeles based Church of Satan, founded in the 1960s, in the sense that these rituals were performed in honor of the Devil and involved a parody of the Church mass. However, LaVey always asserted that his black mass was not intended to defile the Christian God, because he denied the existence of such a God. Since the deliberate degradation and defilement of Christianity is one of the key features of the true black mass, the mass performed in the Church of Satan falls short of perfection.

The concept of the black mass has no meaning outside of Christianity. It was a fantasy created by the priests of the Inquisition as the worst thing they could possibly accuse supposed witches of doing. After it became a part of the literature of the witch craze in various incomplete forms, and was widely accepted as historical fact, it was on rare occasions recreated from these accounts and performed by groups of 18th and 19th century decadents looking for magical power and cheap sexual thrills. The black mass only ever truly existed in all its dark glory in the form of these staged re-creations.

The belief was that the black mass derived its efficacy from the esoteric energy of the Catholic mass perverted to evil ends. In modern times, now that Christianity has lost so much of its spiritual and temporal power, there is very little reason for any group to perform the black mass. It will probably always remain merely an anomaly in the history of the occult.

Those interested in this subject may wish to read H. T. F. Rhodes' The Satanic Mass, published by Rider and Company in 1954, and reprinted by Arrow Books of London in 1973.