So, them Allagans... (possible spoilers)

[Fenral]

(Still hoping that Nero's Aetherometer was picking up a weapons hanger of some kind below the Labyrinth of Ancients and we get to explore it)

I mean, the totally random theory I've put together is that

the Line of Desch (it needs a name) stayed up on Azys Lla up until the Fifth Umbral Era, making its way to Sharlayan via Eorzea around that time by blending in with the Miqo'te migration. Passing through Mor Dhona along the way, the current heir apparent became fully aware of Salina's true plans locked away in his blood, vowing then and there to put an end to the family's oral tradition that it might never come to pass. (Un)fortunately, even without the stories that came with it, there was enough of Allag left in the blood itself that built-in failsafes could start restoring the memories within once the Tower was rediscovered. Whatever is stirring beneath the Labyrinth is not an accident, so much as a necessary part of the plan that must occur before the Tower can be used to restore Allag's "hope."

I just have a feeling that someone supposedly privy to all the Tower's secrets, and supposedly shutting it down completely, would be unaware of second power source underneath.

Everything working out according to Allag's "destiny" needs to get deconstructed badly before I let any of it go.

I have a feeling this is tied to Nidhogg in some way, or to one of the Great Wyrms at the very least. That giant broken neurolink in the Aery is STILL entirely unexplained and is likely a missing piece in understanding what actually happened on Azys Lla.

It's supposedly a piece of Dalamud that somehow traveled farther than any single other piece of wreckage, according to Yoshi-P, but that just screams government cover up. There's an entire page in the Heavensward artbook detailing the Allagan wreckage there, and none of it is labeled. A loose bit of Binding Coil with no significance whatsoever would have just been pulled from the T11 assets, not created from scratch.