So, I stumbled across the .txt file for a thread I made a while back, and it got me thinking about the events of 2.5 in a new light.
Let's start with perhaps the most confounding question: Are the Crystals of Light Hydaelyn's blessing?
At first I wasn't sure that they were directly Hydaelyn's blessing. However, our interactions with Midgardsormr made me reconsider that. Specifically, when he seals the Crystals he says that he has stripped us of her blessing, and he rather seems to know what he's talking about. So, I'm willing to take Mid at his word. On the other hand, the next question complicates things somewhat. . .
Next question: Mechanically speaking, how was the blessing stripped from us?
For reasons I'll explain shortly, I think that the Crystals of Light were completely sealed. That is, sealed from Hydaelyn, sealed from us, and sealed even from Mid (though I assume he can undo it if he really needed them). Now, I have reason to believe that certain things associated with the Crystals predate our encountering them. I'll go into those reasons in the next section. If it's true, though, it means that Hydaelyn (presumably) was interacting with them before we found them. I suspect that simply having their presence in the life stream was enough for Hydaelyn to utilize them, and that Mid's sealing them has temporarily removed them from the stream entirely.
Wait, now! What's this about Hydaelyn using the Crystals before we came across them?!
Well, here's the thing. Tupsimati has been hanging in the Waking Sands for five years before the start of the game. During all that time, at no point did any of the Ascians stroll into the base and take it. This is five years in which the Crystals of Light are scattered to the four corners of Eorzea. If there were no seal during those five years, it would mean that Nabriales chose not to seek one of the most potent artifacts we've seen in game during that time. Much more likely, I think, is that there was already a seal present shortly after the Calamity. The problem is, when Mid seals the Crystals, that breaks the seal. That implies that the seal is founded on the Crystals. But the crystals have been scattered for the last five years, during which time it seems logical to conclude there was a seal. Ergo, I think Hydaelyn was using them even when they were scattered in order to power the seal.
Well, how the heck is Hydaelyn supposed to do that?
Here's where it starts getting. . .weird. Initially, I thought that maybe Hydaelyn was able to move aether from the Crystals of Light over vast distances. After all, at the beginning of the story we can only "confirm" that three of the Crystals were unpossessed by Primals. While Ul'dahn players would have seen the Crystal of Water in the desert, for others it was either in La Noscea or the Black Shroud. In fact, for a Gridanian player the closest Crystal known not to be possessed by a Primal is still extremely far from the Waking Sands, to put it mildly. We might assume that the Crystal of Fire had not yet been consumed by Ifrit, but that is still kinda far from the Waking Sands, even if we place it in the mines of Western Thanalan.
But even our most restrictive reading, putting an unconsumed Crystal of Fire within Copperbell Mines, is still a little ways to be moving that much aether. If Hydaelyn is capable of that, then why would she not use the vast, vast quantities of aether within Mor Dhona to replace the seal when deprived of the Crystals of Light? Was the power of just three Crystals of Light, even attenuated by nearly a full continent's distance, still more powerful than all the aether of Mor Dhona? I'll grant it's possible; we still know extremely little about the Crystals, after all. I suspect, though, that it was a different quality of the Crystals that made them valuable in constructing the seal.
When we defeat Primals, their aether returns to the land. Logically, this would include the aether of all the crystals consumed in their summoning. Of note, though, the Crystals of Light do not disperse. I suspect, therefor, that part of what makes the Crystals unique is their stability. Regardless of how much we or Hydaelyn have used them; despite being heaped with other crystals as sacrifice for Primals; even when channeled to shield us from Ultima, the Crystals of Light have shown no signs of ever being truly consumed. This, I think, is what Hydaelyn was counting on when she used them as the basis for the seal.
It also, I think, can potentially address another issue with the seal. Specifically, if the seal is based on the Crystals of Light, and we're traipsing all over the continent with them, how does the seal not fluctuate? The best I can come up with is that the Crystals have a constant presence within the stream. That is, no matter where they're being moved within the physical world, possibly including into Primals, they aren't budging within the flow of aether. It's only when Mid decides to completely seal them from the stream that things break down. Of course, there's still the problem that Tupsimati becomes a moving target for however long it takes to move bases, so maybe I'm over thinking matters. Regardless, though, the seal is fine up until Mid plucks the Crystals from the stream.
New topic: Why are Nabriales and Minfilia the only ones to notice the change?
Minfilia notices by the end of your first conversation that something's changed. Nabriales notices pretty quickly. Furthermore, he puts two and two together and realizes that the seal is also broken. Since a lot of what we know about the Crystals of Light came from the Ascians, I'm not surprised that they know more about the seal than we do. In fact, I'm pretty sure this is the first time that a seal over our headquarters is even mentioned in the game. Of course, I just realized why the other Scions don't realize the blessing has been taken from us. I keep forgetting they don't have the Echo and don't commune with Hydaelyn. Then again, neither do the Ascians. Good thing Nabriales was more interested in glory than in working with the other Ascians. If he had told the others that the seal was broken, Tupsimati would probably have been taken by now.
On a final note of something that occurred to me as I was coming up with this, the end-of-patch teaser quotes keep hinting that a brighter light casts darker shadows, implying that part of why the Ascians keep ramping up their game is because we're becoming more and more powerful. The thing is, Hydaelyn's been weakened since Ultima. If there truly is a light getting brighter, it isn't her. We defeated Leviathan, Ramuh, and Shiva while she's been recuperating. I think we've become stronger than we realize. Midgardsormr may have broken the seal over Tupsimati, but the first Ascian to try to capitalize on that has died permanently. We can't even be sure the Ascians as a whole have even noticed that he's gone, because as far as we know an Ascian death is unprecedented.
Anyway, at this point the floor is open to hole-poking, so to speak. Let me know if I've overlooked anything or misinterpreted something that should be obvious.