Magus Lynius Shadee says the demon could possess parishioners and drive them to suicide.
He claims to have instructed the evil spirit to "dwell" in the famous church to "cleanse it".
The occultist, who calls himself the King of All Witches, says he let loose the entity to prey on worshippers at the Church of Our Lady and the English Martyrs in Hills Road.
Fr Dick Healey has branded the occultist "twisted" and plans to report him to the police for practising witchcraft in a church.
He said: "He should be reported to the police. It's as if someone came into your home and performed some sort of magic trick without your permission.
"He's obviously a bit twisted to perform witchcraft in a church.
"We will not be performing an exorcism, but I will consider reporting him to the police."
Mr Shadee, a Frenchman with an occult centre in Normandy, claims to have made the "incantation" to evoke the demon on a visit to the city to look for a site for his occult centre, which he plans to open on December 24.
He said: "It's an element, a hunter that will attach itself to an individual, then try to take the person, either send them insane and make them depressed, and the worst is to cause them to take their physical life.
"I did not speak to the priest, just performed a visual ritual format, an incantation, to bring in an element to dwell within the building.
"When I perform, unless it's within the confines of a ritual room, most of my work is on my own with associates observing."
Fr David Paul, of St Laurence's Roman Catholic Church in Milton Road, fears the occultist's move into the city is to target university students, as the News reported.
Now the witch hopes to "convert" the priest.
He said: "I will have to visit Mr David Paul's church and perform a ritual for him - perhaps he will be converted."
Police said a potential crime under the Public Order Act could have been committed if anyone was in the church at the time of the ritual and was alarmed or distressed by it.
