From Lifesite:
On October 13, 1884, Leo XIII had a terrible vision of the assault of the powers of Hell against Holy Mother Church, and ordered the prayer to Saint Michael the Archangel to be said at the end of Mass. He also composed an Act of Exorcism and ordered it to be inserted into the Roman Ritual, and explicitly mentioned what he had seen: “The Church, the Spouse of the Immaculate Lamb, has been filled with bitterness and inebriated with poison by her crafty enemies, who have laid impious hands on her most sacred possessions. In the place where the See of Holy Peter and the Chair of Truth has been set up as 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.”
I should like to ask you all to pray together, using the form given by Leo XIII, the Exorcism against Satan and the Apostate Angels (Exorcismus in Satanam et angelos apostaticos, Rituale Romanum, Tit. XII, Caput III), at three o’clock in the afternoon, Roman time (15:00 hours, Central European Summer Time) on Saturday April 11, 2020, so we can all fight together the common enemy of the whole human race [Latin here, English here].