Exorcism
In Christianity, exorcism is the practice of casting out demons. In Christian practice the person performing the exorcism, known as an exorcist, is often a member of the Christian Church, or an individual thought to be graced with special powers or skills. The exorcist may use prayers and religious material, such as set formulas, gestures, symbols, icons, amulets, etc. The exorcist often invokes God, Jesus and/or several different angels and archangels to intervene with the exorcism. Protestant Christian exorcists most commonly believe the authority given to them by the Father, Son, and Holy Spirit (the Trinity) is the source of their ability to cast out demons.
The Exorcist (novel)
The Exorcist is a 1971 horror novel by American writer William Peter Blatty. The book details the demonic possession of twelve-year-old Regan MacNeil, the daughter of a famous actress, and the two priests who attempt to exorcise the demon. Published by Harper & Row, the novel was the basis of a highly successful film adaption released two years later, whose screenplay was also written and produced by Blatty, and part of "The Exorcist" franchise.