Cyprian of Nicomedia (d. 304), an Antiochian pagan (or pagan Antiochian, depending on your point of view), was a sorcerer who conjured demons, spoke with Satan, and lived for a time in Memphis (the trifecta of third century evil). Justina was a devout Christian maid determined to stay that way, and when she refused to accept a certain Agalides’ marriage proposal, he sought the sorcerer’s aid. Thrice Cyprian sent demons to inflame her with the passions of the flesh (chocolate, ice cream straight from the carton, etc.), but thrice she made the sign of the cross and they were vanquished. He also tried to call down pestilence on her family, neighborhood, church, greengrocer, etc., but her prayers turned it aside.
Not long thereafter, Cyprian said to the Prince of Darkness, “If the sign of the cross can defeat you, how will you be able to stand before Christ himself?” Satan flew at him in a rage, but Cyprian, as something of an experiment, made the sign of the cross, and the devil was defeated. “Whoa, this is some powerful juju,” he said. The next day he went to the local bishop, gave his magic books to help defray the church’s heating costs, and was soon baptized. He progressed through the priestly orders until he was a bishop, all the while converting oodles (to use the correct technical term) of pagans.
When Diocletian began thinning the Christian garden, Cyprian and Justina were brought to trial and after various torments condemned to lose their heads over their religion. Cyprian feared Justina would lose her nerve if she saw him killed, so he asked for time for prayer, during which Justina was martyred. Seeing all this, the soldier Theoctistus declared himself a Christian, and he and Cyprian were beheaded together. Their story was known to Gregory Nazianzen (d. 390), and ancient versions exist in Syriac and Ethiopic.
Guardian Angels. The belief that every person has an angel watching over him or her goes back into the shadows of antiquity (which would be a great name for an oldies cover band, right?), even to the ancient Babylonians and Abyssinians and guys like that. The Old Testament hints at it, and the medieval Rabbi Rashi (d. 1105), speaking of a man terrified of something he cannot see, says, “His guardian angel, who is in heaven, does see it.” Muslims believe that every Muslim has not one but two guardian angels, who work in shifts: one watches over him (or her) by day, and one by night. Which is less parsimonious, but definitely touching.
Christians anchor their belief in guardian angels in the words of Jesus (Matt. 18:10), who, in reference to a passel of children, said, “[I]n heaven their angels do always behold the face of my Father which is in heaven.” The belief is strengthened by the Epistle to the Hebrews (1:14), which speaking of angels says, “Are they not all ministering spirits, sent forth to minister for them who shall be heirs of salvation?” (Hint: this is a rhetorical question; the answer is “Yes.”) In the Acts of the Apostles (12:12 ff.), the apostles mistake Peter for “his angel,” hinting that the guardian angels may even look like the people they guard (how your intrepid hagiographer pity his if that’s the case!).
Today’s feast was present in various locales early on. Pope Paul V was the first pope to establish the feast, in 1608. In 1883 was declared a “double major” (philosophy and accounting) by Pope Leo XIII. Many people of course pray to their guardian angels in times of trouble (and even in times of untrouble), a practice defended by one wise child of my acquaintance who, when challenged on this point, asked, “So you’re telling me I have a guardian angel in heaven who constantly looks over me, guiding and guarding me every moment of every day, but I’m not allowed to talk to him?”