What is the "Illumination" or Warning?

The event has been prophesied by several holy men and women. It is a "warning" to put oneself right with God before the coming purification of the world.

St. Faustina describes an illumination she experienced:
    Suddenly I saw the complete condition of my soul as God sees it. I could clearly see all that is displeasing to God. I did not know that even the smallest transgressions will have to be accounted for. What a moment! Who can describe it? To stand before the Thrice-Holy-God! —St. Faustina; Divine Mercy in My Soul, Diary 
    I pronounced a great day… wherein the terrible Judge should reveal all men’s consciences and try every man of each kind of religion. This is the day of change, this is the Great Day which I threatened, comfortable to the well-being, and terrible to all heretics. —St. Edmund Campion, Cobett’s Complete Collection of State Trials…, Vol. I, p. 1063.
      Blessed Anna Maria Taigi (1769-1837):
      Known for her astoundingly accurate visions, also spoke of such an event. She indicated that this illumination of conscience would result in the saving of many souls because many would repent as a result of this"warning"… this miracle of "self-illumination." —Fr. Joseph Iannuzzi in Antichrist and the End Times, P. 36

      Mystic Maria Esperanza (1928-2004):

      The consciences of this beloved people must be violently shaken so that they may "put their house in order"… A great moment is approaching, a great day of light… it is the hour of decision for mankind.—Ibid, P. 37 (Volumne 15-n.2, Featured Article from http://www.sign.org/)
      Also see: