Another theory I saw earlier on in the topic was the prison Dalamud was the one absorbing the aether of the failed primals such as Garuda and Ifrit. As the ending FMV ended, a horse whinnying, a screech and some low growls could be heard. This may be stretching it, but it heralds that at least, at the end, Odin and Garuda and Ifrit came to the scene of destruction. But how?

Since the prison was blown up by Bahamut's megaflare, the pieces of the prison slammed into the ground. The remaining aether leaked into the ground. We see pieces of the prison weakening in the beginning hitting Coerthas, and we definitely see the remains of the prison slam into Thanalan. Since the primals draw on the aether, would this have awakened the primals from their abstract state?

It remains a question whether it was the prison was the one absorbing aether to maintain it's function, or was it Bahamut absorbing it. It could be both, aether filtering through the walls in order to reach Bahamut. As the ending implies that the Twelve was the one who originally sealed Bahamut in the prison, and the Twelve required aether for their work, that also would imply that the prison needed aether to maintain it's seal. And Bahamut being a primal at it's core would need aether to grow stronger as well.

About Althyk's role in this; it seems that just because Louisoix could use Althyk's glyph doesn't mean he's the only person capable. What if the whole Circle of Knowing could use it, seeing as Echo is a deep measure of them? Would that mean the players, as a result of Echo, also gain the ability to manipulate time? (maybe even herald the lore inclusion of Time Mage)

This was a lot of information to digest - I'm going to bookmark this thread and slowly absorb and categorise events in my own notes.

Oh, and for lore hunters, there are a few continents/landmarks mentioned ingame that I picked up. You may or may not have them in your notes, but sharing is caring.
- Meracydia
- Gardens of Xarakish
- Floating Lakes of Voor Sian Siran