But Mary's power over the evil spirits will especially shine forth in the latter times, when Satan will lie in wait for her heel, that is, for her humble servants and her poor children whom she will rouse to fight against him. In the eyes of the world they will be little and poor and, like the heel, lowly in the eyes of all, down-trodden and crushed as is the heel by the other parts of the body. But in compensation for this they will be rich in God's graces, which will be abundantly bestowed on them by Mary. They will be great and exalted before God in holiness. They will be superior to all creatures by their great zeal and so strongly will they be supported by divine assistance that, in union with Mary, they will crush the head of Satan with their heel, that is, their humility, and bring victory to Jesus Christ. 

St. Louis de Montfort - "True Devotion to Mary"