So, quite a long patch, but I've managed to get through it all. I'll go through the areas which caught my interest.
Elidibus
Yoshi had mentioned during the interviews that we'd need to approach him for information, but that he will be quite hostile for the time being, assuming the worst had come to pass. He is indeed not willing to pause and exchange pleasantries this time... and he does not seem to agree with the Scions' interpretation of Emet-Selch's final exhortation, and is resolved to see the Convocation's plans through. Given that part of the Convocation is Zodiark, and not just that but someone from the very office he now serves under, I think that's what he means by enforcing the "Will of the Convocation".
His plan is rather clever, and is in line with what I expected - he's trying to revive the Flood. To openly oppose him in the Crystarium would be very dangerous, especially after the characters went to pains to revive the First's WoLs' reputation. The method he used differs to what I thought it'd be, but the starstorm illusion seems to have "activated" the Echo in the onlookers at the Crystarium and he confirmed what I and others had thought about it, i.e. that it's the hallmark of once being an unsundered soul. I'm not sure if it went as far as to imply that all souls are sundered ancient souls (certainly possible, with varying degrees of dilution/enervation given the course of the Lifestream, and yet it seemed like not everyone had it awakened), but at this point it's not as important as what it is precisely. Whether Hydaelyn's words were also part of the illusion, or whether she emits a "signal" at all times in all directions on the Source and the Reflections, to lure in those whose Echo is activated, is unclear, but I think it's the latter. That Hydaelyn apparently herself creates illusions or plucks meteors from the heavens to bring about new minions/servants, as Elidibus put it, is intriguing.
I'll make no secret of the fact that he is one of my favourite characters in the game. I still feel that his writing, at least as of the later parts of 4.x, diverged from earlier portrayals of the character, who was more amenable to dialogue and understanding the WoL better. For some reason they seem to have shifted that all to Emet-Selch. Perhaps 5.3 will pick up on it and he is just tight-lipped because he sees no room for negotiation right now, and also because of the legacy of his office, being at the core of Zodiark's summoning. That said, I think they did a good job in conveying both his stoic determination and grit but also a sense of weariness and wariness, especially with the way his expressions shift. His voice acting is awesome. He's definitely in no mood to play games and views the Scions' interpretation of Emet's words as silly, becoming rather annoyed at the very notion of what they're suggesting. I agree that it probably is not what Emet had intended to say. I think Emet was bidding the WoL - being a sundered ancient soul and an Amaurotine he once knew, at that - to seek out the truth of their past.
Y'shtola doesn't seem to think it's as simple as him being the successor to the original "Elidibus", so I am now curious what this means if her intuition is correct, and who/what he truly is. An idea which springs to mind is that he may be some kind of manifestation of the man in Zodiark's "heart". At the very least, the symbol of the office, shown on the crystal in the artwork for 5.2, is of some significance according to the interviews in relation to his role as arbiter... whether that means the Elidibus-in-Zodiark, or Elidibert (or perhaps even a projection of the original), remains to be seen. I've long wanted to hear from Zodiark himself, so I'm hoping that we will, even if it's original Elidibus.
Anamnesis Anyder
Really well designed dungeon, both the trip to it and the actual ruins. It apparently functioned as an archive, and apparently a repository for concepts, presumably after the Bureau of the Architect had reviewed them, and linked to Akadaemia Anyder. Having the Benthos shaman tap into the concept vessels to invoke monstrosities from them (the term "ousia" meaning "essence) was a nice touch. It did have some very hefty reveals, casting some further light on what happened after Zodiark was summoned... so it seems like the departed member of the Convocation was not amongst Hydaelyn's summoners, who were led by Venat (and for a variety of reasons, this does not seem to be the main character, especially given the function which Venat serves), and also did not even answer their calls. Apparently in the JP version the voice actress for Hydaelyn matches Venat's, which is a nice touch.
Furthermore, even the leader did not wish to malign the Convocation for doing what it saw fit to protect the star... there wasn't bad blood per se but it was a disagreement over providing a permanent solution to this calamity that, as yet, remains a mystery. What struck me was the reason cited, i.e. that Zodiark was not a permanent solution to the problem facing them even if he did afford them reprieve. Venat does not mention sundering as an objective, nor do they mention the reason Hythlodaeus gave i.e. the final stage of intended sacrifice (although perhaps it was there in the back of their minds and what they ultimately meant), but specifically the reason Emet-Selch gave, i.e. to check Zodiark's power. They also mention their course would earn them the undying condemnation of their brethren.
We are told the Convocation did not wish to consider a "permanent solution" and the departed member of the Convocation was none too interested, either, so I submit that there is the possibility the solution may have been deemed worse than the problem it sought to solve. I get the impression that they intended to make the Convocation and other ancients listen through shackling Zodiark, and thus, whilst well-intentioned, we're resorting to an extreme measure. On reflection, the Sundering does seem to be exactly the sort of action that would earn them their people's condemnation and maybe it was implied in "checking" Zodiark's power, but at the same time maybe the mere act of summoning Hydaelyn to be his shackles could serve to do that, and maybe it spiraled out of control thence, leading ultimately to the Sundering. Elidibus's epilogue at 5.0 gives the suggestion that it may have been intended all along, but it's not categorical. Still, given that Zodiark was the Will of the star by then, thus inside it, and given that she possessed the ability to sunder, surely it must have been foreseen as a possible outcome? Moreover, in the case of both summonings, what was the departed member's alternative, particularly in Zodiark's case given their impending doom?
Also, it's worth noting Hythlodaeus had suggested Hydaelyn's summoners surrendered their life energies to bring her about. Odd that the diplomatic ancient should then say of Venat that she'd be missed - by whom, since they went on to summon Hydaelyn and presumably died in the process? I'm aware the JP version of Hythlodaeus's dialogue differs a bit on that point (saying something like "from their own power"), but not to the point where it would outright contradict the English version. Just worth noting in any case. Regarding Elidibus, I wonder at this point if the whole "Heart of Sabik" thing is important because that is who the Elidibus who became Zodiark's "heart" was, assuming he was not the very first occupant of the office (in which case it'd have been named after him.) As for the Elidibus we're dealing with now, assuming Urianger is correct that the original was replaced, it could be the departed Convocation member, but I still think they're going for a parallel between this individual's apparent distaste for Primals, and the current WoL's role as the Eikon slayer. It'd allow for the ancient protagonist's soul to occupy a neutral position that has been sucked into a war between Primals since the Sundering, at the very least in recent times. Also, if current Elidibus were the departed member, it'd make more sense to return to his original office assuming a replacement was not already found. The "diplomatic ancient" is also a possibility depending on whether the English version of Hythlodaeus's account of what happened to the summoners is accurate and this may explain why Elidibus has so much knowledge about Hydaelyn's summoners, and also explain quirks like Nabriales restraining himself from killing Minfilia because it'd anger Elidibus.
With what we know from the end of Eden (i.e. Ryne becoming the vessel for Shiva's summoning), I think it is entirely possible that things went in unexpected directions. The ancients were still somewhat new to creating these beings, which were explored as a method to deal with the sound that would later bring about Terminus and the Final Days, so it's possible that at that point they would not have expected a Primal with someone summoned at its core to deviate so from its original purpose. Perhaps they did so deviate, especially once they began fighting with one another.
Ryne took on a form very reminiscent of Hydaelyn, what with the double halo, the wings, the kick, and so on, maybe because of the knowledge she inherited from Minfilia/what she saw on the cave walls, but what if this Venat, and original Elidibus, both became corrupted by the amount of light and dark aether, respectively, to the point that they really believe themselves to be gods locked in some war? If it could happen to Ryne, the same could to an ancient, with a sufficiently powerful Primal like either Zodiark or Hydaelyn. Thus perhaps the eventual introduction of an arbiter to the storyline, as 5.0 closed by asking by what hand could this war between light and darkness end. So far, the WoL is playing for Hydaelyn, but to what extent have they become engrossed in a case of massive Primal summoning gone wrong? I'm eager to see how they position this. Lastly, the presence of a person within the Primals might mean they don't use tempering to control the tempered in the same way that other Primals might but only draw upon it when necessary.
Zenos
Taking the white-robed character's words at face-value, it does not seem like he had a first hand account of the Final Days, so I still think he's probably some WoD or Ascian, of the sundered variety. Perhaps loyal to Elidibus, to ensure things proceed apace on the Source, since if he succeeds on the First, he will need the Source to be primed to draw on its aether, and it would be uncharacteristic for him to just leave this to Zenos's whims. That Zenos himself had visions of the Final Days is intriguing, and perhaps is a sign that Emet-Selch being his great-grandfather did rub off on his aether since this did not start with the Resonance but is something he "always" saw (so guessing this means since childhood.) The majority of Garlean Purebloods may not be able to wield aether into magic but assuming that they too, like everyone else, are sundered forms of ancient souls, at the least some should have the potential for the Echo "written" into the aether composing them. Their physiology is probably what hinders it. I'm wondering if the difference here is Zenos's unique lineage, resulting in him inheriting a memory of the Final Days... or if Emet otherwise implanted it in him somehow, as Zenos's new friend speculates. Also, with the revelation that there is some person at the core of Zodiark and Hydaelyn, that could be how he ends up taking over Zodiark and fusing with him. Although the presence of a conscious will in the "heart" could make it more difficult, it does sound like something Zenos would slot into.
Given Venat's role and style in XII (plus the reference they pulled with Nael's Legion and the Meteor; Zenos was Legatus of the 12th) and its interaction with Vayne, it crossed my mind that this could be who this character guiding Zenos is, but this has some difficulties given that they're still presumably Hydaelyn's core... unless of course this all were to be facilitated through a minion, or some manifestation of Venat's. It seems like they're playing up XII Venat's opposition to its peers (and the destruction that later ensued), rather than the angle of its penchant for aiding mortals to achieve its own ends, but at this point the latter can't be ruled out. Yet if Venat could approach him, why not the original Elidibus? "Venat" is connected to the Latin verb for "to hunt", coinciding with Zenos's main obsession, so there's also that. Either is possible, I suppose, depending on how they want to play it, and it does seem to me that he's being primed to be used by one of them, one way or the other.
Ruby Weapon
Not too much to say on this, other than that it's nice to see them showing a different side of Gaius and giving him even more personal investment in this whole storyline, in addition to his guilt for his past and love for his homeland, and the agreement he made with the Elezen in spite of it. The Gundam references in the fight with the Oversoul, and the freaky nature of the whole device (which almost seemed to be creating a synthetic Primal of sorts, by draining the pilot's life force), were epic touches. I do hope we're going to Garlemald next, so I'll be keeping an eye on where the plot goes with this. Fun fight, and I loved the Nael transition. Keen to see which programming they use for future fights - maybe we'll see an interpretation of Emperor Solus.
Eden
I didn't find Gaia to be that endearing as a character, but she was alright and improved towards the end. Urianger's explanation about the change in the First's aetheric balance, to become more active, enabling Zodiark to call upon a measure of his power, is sensible and probably true, especially given the icon's shape, which is reminiscent of Zodiark's form. Still, the voice did remind me a bit of a Voidsent, when it said to her it hungered, and then bade her to awaken their power, but it may just be a stylistic similarity in the end.
Either way,
this looked like a strong pointer to the identity of the "Oracle" being some interpretation of Ultimecia.
The boss fights themselves were a lot of fun, very fast-paced and had great mechanics. I especially liked E6 and E7, with the icon commandeering both darkness and light, and E8 was indeed very visually spectacular. I really liked the "unexpected" arc of Garuda and Ifrit fusing and the way they arranged their original themes.
It felt a bit bolted on to have Urianger and Thancred simply announce they're leaving the First at the end but I guess we'll get the detail later on.