Today is traditionally both the feast of St Mark the Evangelist, and the observance known as the Greater Rogations. The latter is a penitential procession instituted by Pope St Gregory the Great at the very beginning of his reign (590 A.D.), to beg God’s mercy for the end of a terrible plague that struck Rome and environs, and killed his immediately predecessor, St Pelagius I. Although the plague and the institution of the procession are well attested facts, various legends accrued to them over time.
One such legend is that the Pope divided the populace into seven groups, which were to start processing towards St Peter’s Basilica from seven different parts of the city. When the seven processions converged at the Pons Aelius, the Archangel Michael appeared over the tomb of the Emperor Hadrian and sheathed his sword, a sign that the plague was over, just as happened to King David. (2 Samuel 24). Because of this episode, the late medieval fortress which was built over the tomb is now known as the Castel Sant’Angelo (castle of the holy angel), and the bridge in front of it as the Ponte Sant’Angelo, and to this very day, there is a statue of the Archangel Michael on the top of the tomb.
A Dominican friar named Jacopo da Voragine (1230 ca. – 1298), who became the archbishop of Genoa in 1292, produced a famous collection of such stories known as the Golden Legend, and include this tale about the origin of the plague, one of several in which dragons play a prominent role.
“The Tiber river once overflowed its banks so far that it came over the city walls and destroyed a great many of houses. Then also a multitude of serpents with a great dragon came down by the Tiber river to the sea, but were smothered by the waves and cast onto the shore, and with their corrupted all the air.
And thus, the terrible plague which they called “the groin plague” (i.e bubonic) followed, so that arrows were seen coming down from heaven and striking various people. And first of all, it struck Pope Pelagius and killed him at once, but afterwards, raged through the population so fiercely that it left many houses empty in the city, since their inhabitants had been killed.
But because the Church of God could not be without a leader, the people unanimously elected Gregory, although he made every effort to refuse. Therefore, since he had to be consecrated, but the plague was devastating the people, so he preached a sermon to them, and organizing a procession, he instituted the litanies, and exhorted everyone to beseech God the more intently. While the entire people, being gathered together, besought God, the plague itself raged to greatly that in one hour ninety men died; but Gregory did not in any way cease to urge all the people to persist in prayer, until the divine mercy should drive away the plague.”
(The Procession of St Gregory the Great, by an anonymous Sienese painter of the mid-16th century.)