"Our Lady showed us a great sea of fire which seemed to be under the earth. Plunged in this fire were demons and souls in human form, like transparent burning embers, all blackened or burnished bronze, floating about in the conflagration, now raised into the air by the flames that issued from within themselves together with great clouds of smoke, now falling back on every side like sparks in a huge fire, without weight or equilibrium, and amid shrieks and groans of pain and despair, which horrified us and made us tremble with fear. The demons could be distinguished by their terrifying and repulsive likeness to frightful and unknown animals, all black and transparent. This vision lasted but an instant. How can we ever be grateful enough to our kind heavenly Mother, who had already prepared us by promising, in the first Apparition, to take us to heaven. Otherwise, I think we would have died of fear and terror."Source: Wikipedia
