Originally Posted by
Anonymoose
The original spell that Louisoix cast was infused with explicit prayers to the Twelve that Dalamud be returned to the sky. It stirred the long-present traces of worship in those areas, and then Louisoix was able to focus it specifically on re-binding Bahamut ("Dalamud") and exiling him again. When Bahamut broke this, it broke the entire focus, so all that was in the air was a massive amount of free-floating aether.
That aether then reacted with the prayers of thousands and thousands of people below, "I don't want to die. Please, let Louisoix save us." This focused all of that aether on Lousoix himself and transformed him into a deiform. This is where I have a big ? even in my headcanon. Did he technically die somewhere in here? Did Bahamut light him up? Did the aether flooding him instantly tear him apart and put him together? That would explain the vision, I guess.