When a Satanic group planned to hold a “black mass” at Harvard University this spring, Catholics around the country joined in prayer to forestall the event, which was cancelled.

Now that a different Satanic group is planning to stage the ritual at a public venue—which claims the Constitution requires them to allow it—the cathedral church of Phoenix, Arizona, is pledging to enter a spiritual battle against it.

Father John Lankeit, rector of Ss. Simon and Jude Cathedral in Phoenix, is urging local Catholics to attend a Holy Hour and rosary prayer service this Friday in response to the “black mass” in Oklahoma City.

Archbishop of Oklahoma City Paul Coakley has said the black mass was meant to offend much of the state’s community.

“There are common standards of decency that civic-minded people uphold that are necessary for constructive public discourse, and this violates all of those standards,” he told Catholic News Agency July 16. “This is a mockery of one faith, a hostile act toward a significant faith community, the Catholic community.”

It would be “truly offensive to a significant segment of their population, that is the Catholic, and the Christian community at large,” the archbishop added.

The occult group Dakhma of Angra Mainyu has scheduled to hold the black mass at the Oklahoma City Civic Center Music Hall Sept. 21. A black mass is a sacrilegious ceremony that invokes Satan and mocks the Mass, involving the desecration of the Eucharist, generally by stealing a consecrated Host from a Catholic church and using it in a profane, sexual ritual.

Archbishop Coakley said that he hopes that through prayer and through continued communication with local civic officials, "they will come to recognize this is not a prudent course, not a good course, for the city.”

He speculated that if someone desired to rent the civic center to have a public burning of a Quran or a blatantly anti-semitic program, the city would "rightly find some way to prevent that from happening. And they should.”

Making “black masses” open to the public exposes people to serious evil, an exorcist warned in an interview with Aleteia last month.

Archbishop Coakley concurred.

"I think one of the things people need to realize, is this is inviting very dark and evil forces into our community," he said. "I think I have an obligation, we have an obligation, to do what we can do to prevent that from happening—unleashing spiritual influences which are harmful and destructive.”

He said he hopes to meet "in the near future" with civic official about the Sept. 21 event. “Obviously for us as people of faith, as Catholics, we’re praying for a change of heart, that something will shift, and that there will be a change of direction, and a recognition that this cannot be allowed.”

Archbishop Coakley noted that there have been a number of petitions against the event on Facebook and other sites, not organized by the archdiocese, but “very much a grassroots thing.”

“My role in this,” the archbishop said, “is simply to provide a voice, and leadership, drawing attention to it, and encouraging people to pray, and to voice their concern to civic officials.”

Should the black mass not be canceled, the archbishop said the Catholic community will “find a way to lift up the Eucharist in a way that shows our love for Christ in the Eucharist, our respect and honor for the gift of the Blessed Sacrament.”

Whether through Masses of reparation, holy hours, or processions, “we will do what we can do to bear witness to our faith in the true presence of Christ in the Eucharist.”

The Arizona cathedral holy hour is the first such event to be publicized. Father Lankeit, who will preside, said it will consist of chanted adoration and Benediction hymns, a Gospel proclamation and short homily, a Rosary and "plenty of silence in between for contemplation."

It was in Phoenix where a priest was killed in an apparent burglarly attempt earlier this year. A homeless man and convicted felon pleaded not guilty last Thursday to charges of killing the priest and beating another one with a metal pipe at the downtown rectory where they lived.