We must be frank: spiritually and morally speaking, the world is in a state far worse than it has ever experienced before in history. Common sense testifies to this. The consensus of private revelation indicates this. Even Papal Magisterium teaches this. Pope Francis, himself, has said that we are “no better today than they were during the Great Flood” (February 19, 2019 homily at Santa Marta).
Thus, the Era of Peace cannot be ushered into the world as it now stands. A total renovation is necessary; one that, as it were, strips the house down to its beams and bricks, if not its very foundation. This purification will be achieved in many ways in the upcoming years, but perhaps above all through the long-prophesied Three Days of Darkness, which will definitively cast out evil from this earth (particularly the Antichrist, those who follow him, and the demons who inspire him) and leave it ready for the flourishing of God’s Kingdom.
Unfortunately, most people alive today do not want God’s Kingdom. They would much prefer to continue committing their favorite sins, believing their favorite errors, and relishing their favorite grotesquerie. They will be given every chance to change their ways and choose to place themselves on the right side of the coming Era—especially through The Warning (which will precede the period of the Chastisements and certainly the Three Days of Darkness, which concludes it and ushers in the Era of Peace). But if those who reject God’s Kingdom continue to refuse to repent, there simply will be no room for them on this earth during the Era, and if no other Chastisements do the job before the time comes, the Three Days of Darkness will.
(Nota Bene: We must never lose hope for the salvation of anyone alive; no matter what. We should even hope for and pray for the salvation of those who ultimately will need to be purged from the earth in the Three Days of Darkness—for even if their failure to repent before that time required their being purged from the earth, this does not mean that they cannot repent in their life’s last moment. See Mark Mallett's Mercy in Chaos)
The Three Days of Darkness, in brief, will consist in all of hell being unleashed upon earth in order to allow the demons to devour their own who are upon earth—for, with great irony, not even the demons can resist God’s will (although they receive its justice, while the blessed receive its mercy). When God unleashes the evil spirits to purge the earth, they will not be able to do one iota more than He has ordained before they are cast back again into the abyss.
Even the demons are checked by good angels lest they harm as much as they would. In like manner, Antichrist will not do as much harm as he would wish. —St. Thomas Aquinas, Summa Theologica, Part I, Q.113, Art. 4
So the faithful must not fear the Three Days of Darkness; although its enormity would boggle anyone’s mind, it will be undertaken with the precision of an expert surgeon due to God’s providential oversight. Moreover, as God protected the Israelites, so too will He safeguard His remnant.
Moses stretched out his hand toward the sky, and there was dense darkness throughout the land of Egypt for three days. Men could not see one another, nor could they move from where they were, for three days. But all the Israelites had light where they dwelt. (10:22-23)
Although all of this may sound surprising to those who are learning of it for the first time, we should recall that this paradigm is by no means unprecedented in salvation history and the history of the Church; indeed, one sees throughout both the very enemies of God sometimes being the very ones God uses to bring about His ultimate aims. This happened most clearly in the crucifixion of Our Lord; but one also sees, in Scripture, ancient Israel being purified by the godless peoples surrounding them. In the Three Days of Darkness, God will “make use of” the demons in a more universal way than ever before. They will swallow up not only those on earth who are avowed enemies of God, but even physical places and things that have no place in the Era (for example, Fr. Michel Rodrigue was shown demons swallowing up entire foundations of buildings during the Three Days).
As the Three Days of Darkness will follow the Warning and the Time of Refuges and culminate the Divine Chastisements, we would personally advise against getting too caught up in the details of this event, and would likewise caution against fretting about the physical preparations. Unfortunately, the Three Days of Darkness, beyond any other prophecy, has generated undue fear and wild speculation. On the other hand, we should even now know the gist of what is coming; for if it were not God’s will that we know this, then heaven (which can only do His will) would not have revealed the nature of this event to us.
I have told you this so that when their hour comes you may remember that I told you. (John 16:4)
We turn, now, to a mere few of these revelations.
God will send two punishments: one will be in the form of wars, revolutions, and other evils; it shall originate of earth. The other will be sent from heaven. There shall come over the whole earth an intense darkness lasting three days and three nights. Nothing can be seen, and the air will be laden with pestilence which will claim mainly, but not only, the enemies of religion. It will be impossible to use any man-made lighting during this darkness, except blessed candles... All the enemies of the Church, whether known or unknown, will perish over the whole earth during that universal darkness, with the exception of a few whom God will soon convert. —Blessed Anna Maria Taigi (d. 1837)
Quoting particulars, Rev. R. Gerald Culleton writes in The Prophets and Our Times:
There shall be a three days darkness, during which the atmosphere will be infected by innumerable devils, who shall cause the death of large multitudes of incredulous and wicked men. Blessed candles alone shall be able to give light and preserve the faithful Catholics from this impending dreadful scourge. Supernatural prodigies shall appear in the heavens. There is to be a short but furious war, during which the enemies of religion and of mankind shall be universally destroyed. A general pacification of the world and the universal triumph of the Church are to follow. —Palma Maria d'Oria (d. 1863); p. 200
All states will be shaken by war and civil conflict. During a darkness lasting three days, the people given to evil ways will perish so that only one-fourth of mankind will survive. The clergy, too, will be greatly reduced in number, as most of them will die in defence of the faith or of their country. —Sister Mary of Jesus Crucified (d. 1878); p. 206
Summarizing many prophet’s takes on the event, Rev. R. Gerald Culleton writes:
When everything seems hopeless for the Christian forces God will work a "wonderful miracle," or as some prophets refer to it," a great event" or "a terrible event," in favor of His own. During this phenomenon, the truly holy will not be harmed, and terrible though it will be. yet we may take consolation in the fact that it will mark the end of God's chastisements. It would seem that the event mentioned vaguely by so many seers, is that specified by others as three days of darkness with the sun and the moon, as it were. turning to blood. The air will be poisoned, thus killing off most of the enemies of Christ's Church. During these three days, the only light available to men will be blessed candles, and one candle will burn the entire period. However, even blessed candles will not light in the houses of the godless. Yet once the candle is lit by one in the state of grace, it will not burn out until the three day's darkness is over. This "great event" will usher in peace to the troubled world. It would be a sort of reenactment of the three hours of darkness "over the whole earth" at Christ's crucifixion, and a preview of that which will mark the end of the reign of Anti-Christ. —p. 45