In The Pope's Exorcist Russell Crowe's Father Gabriele Amorth faces Asmodeus, a demon possessing a young boy named Henry, who turns out to have a fascinating backstory. The horror film is inspired by the real Father Amorth, a WWII veteran and former journalist who eventually devoted himself to the Catholic Church and became the "Pope's Exorcist." Father Amorth wrote several books about his experience being an exorcist for the Diocese of Rome which inspired the film, including Father Amorth: My Battle Against Satan, An Exorcist Tells His Story, and An Exorcist Explains the Demonic: The Antics of Satan and His Army of Fallen Angels.

https://screenrant.com/popes-exorcist-asmodeus-demon-henry-explained/