Father Merrin is a fictional character from the horror novel and film series, The Exorcist. He is an experienced and elderly priest known for his expertise in battling demonic forces. Merrin is portrayed as wise and compassionate, often reflecting on the nature of good and evil. In the story, Father Merrin is called to perform an exorcism on a young girl named Regan MacNeil, who is possessed by a demon. His character represents the struggle between faith and darkness, showcasing the challenges faced by those who confront supernatural evil.