Mary, "you are terrifying as an army in battle array."
St. John Bosco was a holy Italian priest, the recipient of many supernatural visions from God. In particular, he once saw a vision of the Church in the midst of a great trial, buffeted by many enemies.
St. John Bosco’s prophetic vision of the Church during times of trial
However, in the vision, as long as the Church was tethered between the pillar of Mary, Help of Christians, and the pillar of the Eucharist, the Church would survive. He wrote, “Only two things can save us in such a grave hour: devotion to Mary and frequent Communion. Let us do our very best to use these two means and have others use them everywhere.”
Below is a prayer attributed to St. John Bosco directed to Mary, Help of Christians, that reflects this belief and places a person within the powerful protection of the Virgin Mary against all evil forces acting in the world.
O Mary, powerful Virgin, you are the mighty and powerful protector of the Church; you are the marvelous help of Christians; you are terrible as an army in battle array; you alone have destroyed every heresy in the whole world. In the midst of our anguish, our struggles, and our distresses, defend us from the power of the enemy and at the hour of our death, receive our souls in paradise. Amen.
This is how to keep the devil away, according to St. John Bosco