Why is Mary depicted standing on a snake?

The tradition is based on a verse from the Book of Genesis, in which the downfall of Satan is predicted.

One of the most common depictions of the Virgin Mary has her standing on a snake. Why is that? The tradition finds its roots in a biblical verse that was translated in the Latin Vulgate (which was later translated into English in the Douay-Rheims Bible). In the Book of Genesis, shortly after Adam and Eve ate the forbidden fruit in the garden, God curses the serpent who tricked them and foretells his ultimate destruction.

I will put enmities between thee and the woman, and thy seed and her seed: she shall crush thy head, and thou shalt lie in wait for her heel. (Genesis 3:15)

Initially this was taken by the Church to refer to Mary, the woman who would give birth to the Messiah. It would be through her “Yes,” that Satan would be defeated, and the curse of Eve lifted.

The good news is that Satan, the “serpent,” has been defeated through the sacrifice of Jesus on the cross. Mary’s “Yes” made that possible, and through her free choice our Messiah came into the world.

Mary remains the “Terror of Demons,” and it is no surprise that demons often flee at the name of Mary, fearful of the woman who reversed the disobedience of Eve.