In the Book of Revelation, Michael leads a victorious angelic army against the angelic forces led by Satan. The Catholic church regards Michael as an archangel. In one of two prayers read at the close of Mass in Joyce's time, it invoked him as a defense against evil.

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Oil painting by Guido Reni of the archangel Michael conquering Lucifer/Satan (1636), displayed in Santa Maria della Concezione, Rome. Source: Wikimedia Commons.

Photograph by Michael Jaletzke of a statue of the archangel Michael at the University of Bonn. Source: Wikimedia Commons.