What was the Second Cataclysm?
The Second Cataclysm is understood to be the event at the end of the Chaos War that ushered in the Fifth Age. At that point, the three moons disappeared from the sky and were replaced by another moon– magic as it had been practiced was no more; the constellations were completely changed and clerical spells were no more; and soon after this giant wyrms appeared and initiated the ravaging Dragon Purge. An explanation for these changes was finally revealed in the War of Souls series.