O Glorious Archangel St Michael, Prince of the heavenly host, be our defence in the terrible warfare which we carry on against principalities and Powers, against the rulers of this world of darkness, spirits of evil. Come to the aid of man, whom God created immortal, made in his own image and likeness, and redeemed at a great price from the tyranny of the devil. Fight this day the battle of the LORD, together with the holy angels, as already thou hast fought the leader of the proud angels, Lucifer, and his apostate host, who were powerless to resist thee, nor was there place for them any longer in Heaven. That cruel, that ancient serpent, who is called the devil or Satan, who seduces the whole world, was cast into the abyss with his angels. Behold, this primeval enemy and slayer of men has taken courage. Transformed into an angel of light, he wanders about with all the multitude of wicked spirits, invading the earth in order to blot out the name of God and of his Christ, to seize upon, slay and cast into eternal perdition souls destined for the crown of eternal glory.
This wicked dragon pours out, as a most impure flood, the venom of his malice on men of depraved mind and corrupt heart, the spirit of lying, of impiety, of blasphemy, and the pestilent breath of impurity, and of every vice and iniquity. These most crafty enemies have filled and inebriated with gall and bitterness the Church, the spouse of the immaculate Lamb, and have laid impious hands on her most sacred possessions. In the Holy Place itself, where has been set up the See of the most holy Peter and the Chair of Truth for the light of the world, they have raised the throne of their abominable impiety, with the iniquitous design that when the Pastor has been struck, the sheep may be scattered. Arise then, O invincible Prince, bring- help against the attacks of the lost spirits to the people of God, and give them the victory. They venerate thee as their protector and patron; in thee holy Church glories as her defence against the malicious power of hell; to thee has God entrusted the souls of men to be established in heavenly beatitude. Oh, pray to the God of peace that He may put Satan under our feet, so far conquered that he may no longer be able to hold men in captivity and harm the Church. Offer our prayers in the sight of the Most High, so that they may quickly conciliate the mercies of the LORD; and beating down the dragon, the ancient serpent, who is the devil and Satan, do thou again make him captive in the abyss, that he may no longer seduce the nations. Amen.
V. Behold the Cross of the LORD; be scattered ye hostile powers.
R. The Lion of the tribe of Juda, the root of David, has conquered.
V. Let thy mercies be upon us, O LORD.
R. As we have hoped in thee.
V. O LORD, hear my prayer.
R. And let my cry come unto thee.
Let us pray:
O God, the Father of our Lord Jesus Christ, we call upon thy holy name, and as suppliants we implore thy clemency, that by the intercession of Mary, ever Virgin immaculate and our Mother, and of the glorious Archangel St Michael, thou wouldst deign to help us against Satan and all other unclean spirits, who wander about the world for the injury of the human race and the ruin of souls. Amen.
(An Indulgence of 300 days)
http://www.freifrancisco.com.br/2017/09/prayer-to-st-michael-by-pope-leo-xiii.html
O glorious St. Michael, guardian and defender of the Church of Jesus Christ, come to the assistance of this Church, against which the powers of hell are unchained, guard with especial care her august Head, and obtain that for him and for us the hour of triumph may speedily arrive. O glorious Archangel St. Michael, watch over us during life, defend us against the assaults of the demon, assist us especially at the hour of death; obtain for us a favorable judgment, and the happiness of beholding God face to face for endless ages. Amen.
O glorious St. Michael, guardian and defender of the Church of Jesus Christ, come to the assistance of this Church, against which the powers of hell are unchained, guard with especial care her august Head, and obtain that for him and for us the hour of triumph may speedily arrive. O glorious Archangel St. Michael, watch over us during life, defend us against the assaults of the demon, assist us especially at the hour of death; obtain for us a favorable judgment, and the happiness of beholding God face to face for endless ages. Amen.