I had a thought yesterday. The crisis in the Church has often been compared to the Crucifixion, except in this case it is the Bride of Christ being crucified... Well, what happened at the end of the Crucifixion, after Christ had died? The sky darkened -- Three Days of Darkness. It's a perfect parallel. And then there was a massive earthquake.
Therefore, it is an earthquake or series of earthquakes that will signal the beginning of the end. If a comet is involved it is probably a harbinger of all this. Comets were considered bad omens in the Middle Ages.
The Catholic Restoration / Great Monarch era apparently parallels Christ's brief Resurrection.