God has established only one enmity – but it is an irreconcilable one – which will last and even go on increasing to the end of time. That enmity is between Mary, his worthy Mother, and the devil, between the children and the servants of the Blessed Virgin and the children and followers of Lucifer.
Thus the most fearful enemy that God has set up against the devil is Mary, his holy Mother. From the time of the earthly paradise, although she existed then only in his mind, he gave her such a hatred for his accursed enemy, such ingenuity in exposing the wickedness of the ancient serpent and such power to defeat, overthrow and crush this proud rebel, that Satan fears her not only more than angels and men but in a certain sense more than God himself. This does not mean that the anger, hatred and power of God are not infinitely greater than the Blessed Virgin’s, since her attributes are limited. It simply means that Satan, being so proud, suffers infinitely more in being vanquished and punished by a lowly and humble servant of God, for her humility humiliates him more than the power of God. Moreover, God has given Mary such great power over the evil spirits that, as they have often been forced unwillingly to admit through the lips of possessed persons, they fear one of her pleadings for a soul more than the prayers of all the saints, and one of her threats more than all their other torments.” True Devotion, Nos 50 – 52).
The Spotless Virgin, the Immaculata, has a special “ingenuity” in exposing the Devil’s plans and tactics. Which is why the Devil often uses others – sometimes other Catholics – to try to influence us to abandon our devotion to Mary, or at least to water it down under the pretext that it is “excessive” or “harmful to ecumenism.”
The Devil knows that those consecrated to the Immaculata will be protected in a special way in this time of Apostasy. Which is why he attacks their true devotion. Again St. Louis de Montfort: “Since Mary alone has crushed all heresies, as we are told by the Church under the guidance of the Holy Spirit (Office of B.V.M.), a devoted servant of hers will never fall into formal heresy or error, though critics may contest this. He may very well err materially, mistaking lies for truth or an evil spirit for a good one, but he will be less likely to do this than others. Sooner or later he will discover his error and will not go on stubbornly believing and maintaining what he mistakenly thought was the truth.” (True Devotion, No. 167),