Blessed Anna Maria Taigi (1769–1837) is the most known seer of the Three Days of Darkness and describes the event in this way:

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. He, who out of curiosity, opens his window to look out, or leaves his home, will fall dead on the spot. During these three days, people should remain in their homes, pray the Rosary and beg God for mercy. 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. The air shall be infected by demons who will appear under all sorts of hideous forms.