Every year, on the Orthodox feast of the Dormition of the Theotokos, a monastery on a Greek island experiences a miracle – dozens of snakes come to 'venerate' an icon of Mary.

In a phenomenon that has reportedly been happening for hundreds of years, black snakes begin appearing on the Greek island of Kefalonia between Aug. 5 and Aug. 15, the days when the Greek Orthodox Church celebrates the dormition of the Theotokos (celebrated in the Western Church as the Assumption of Mary).

According to tradition, the miracle of the snakes began in 1705, when nuns of the monastery were about to be attacked by pirates.

Legend has it that the nuns prayed fervently to the Virgin Mary, asking her that she turn them into snakes to avoid capture. Other versions say that the nuns prayed that the monastery be infested with snakes so as to scare away the pirates. Either way it happened, they were spared.

Since then, the small black snakes, known as European Cat Snakes, appear every year just before the feast, and make their way to the walls and entryways of the Church to 'venerate' the silver icon of Mary known as the Panagia Fidoussa, or the Virgin of the Snakes.

The snakes' patterning can produce a small black cross on their head, and they have a forked tongue, adding to the legend that these snakes are marked by the sign of the Cross.  

In recent years, the faithful have taken to transporting snakes to the church in jars and bags, to protect them from being run over by unwitting motorists.

The usually-aggressive snakes are reportedly docile and calm during these days, when they are welcome in the church for Mass and prayers, and disappear from the island completely after the feast until the next year.

Reportedly, the only years the snakes have not appeared on the island were during World War II, and in 1953 - the year of a massive earthquake. Locals now take the lack of the snake's appearance as a bad sign.

Every year, the island celebrates the Theotokos and the miracle with a Snake Festival.