So when the Exarch was explaining how calamities work, he shows 13 shards and shows them one by one glowing with an elemental aura and then a stream of that element overloading on the Source, causing the respective shard to be rejoined. We see Fire, Water, Wind, Ice, Lightning, Earth, and finally a blackish/redish aura corresponding to the 7th Umbral Calamity. Problem is, the 7th UC wasn't caused by aether overloading the Source resulting in a Firestorm/Flood/Hurricane/Ice Age/Thunder Storm/Earthquake etc. It was caused by mankind dropping Dalamud onto Eorzea. Events that were independent of aetheric balance being tipped. We know Bahamut was aspected to Astral (Darkness) and he can draw on the power of the Sun as the Dawn Wyrm (makes sense given his luminescent and brilliant "flare" attacks. So can someone elaborate more?