Fr. Celestine Kapsner (1892 - 1973), was a Benedictine monk of St. John's Abbey at Collegeville, Minnesota, and translated both books into English. The exorcist-author of the first book was a religious priest ordered by his bishop to set forth in writing his decades-long experiences as an exorcist. The editor, Fr. Gieger, kept his name secret, but recounts that he was reputed for his priestly zeal and untiring and heroic sacrifices. He died in 1909, at the age of seventy-seven, remembered and honored as a saintly man.