Exorcism
In Catholic practice the person performing the exorcism, known as an exorcist, is an ordained priest. The exorcist recites prayers according to the rubrics of the rite, and may make use of religious materials such as icons and sacramentals. The exorcist invokes God—specifically the Name of Jesus—as well as members of the Church Triumphant and the Archangel Michael to intervene with the exorcism. According to Catholic understanding, several weekly exorcisms over many years are sometimes required to expel a deeply entrenched demon.
The Exorcist (film)
Both priests witness Regan perform a series of bizarre, vulgar acts. They attempt to exorcise the demon, but the stubborn entity toys with them, especially Karras. Karras shows weakness and is dismissed by Merrin, who attempts the exorcism alone. Karras enters the room later and discovers Merrin has died of a heart attack. After failing to revive Merrin, the enraged Karras confronts the mocking, laughing spirit, and wrestles Regan's body to the ground. At Karras's invitation, it leaves Regan's body and possesses Karras. In a moment of self-sacrifice, the priest throws himself out of the window before being compelled to harm Regan. He is mortally injured. Father Dyer, an old friend of Karras, happens upon the scene and administers the last rites to his friend.