my trashfire burns in white phosphorus

First, I'm going to point at the exact line from Emet-Selch in Shadowbringers: "He tempered us. It was only natural. There is no resisting such power."

I believe this was said in one of the ocular cutscenes, but explicitly in no uncertain terms--the Convocation was tempered. This includes the Unsundered. The tempering was, in fact, so powerful, that even after having their souls cleansed in the Lifestream Convocation members still make 'the best servants' according to Emet-Selch.

Zodiark was not only the first primal, but a primal on a scale beyond fathoming. This was half a star's worth of souls, billions of people. I'd argue that we also see what this tempering looks like in practice with Emet-Selch at The Ladder scene in Kholusia, where he is genuinely moved and expresses admiration of both the Warrior of Light and the people of Kholusia coming together only to be railroaded back to 'but the world as it was was better'.

That was not a natural thought pattern. That was tempering. We see further evidence in how Emet-Selch tried repeatedly to live alongside The Sundered and had only the most negative qualities amplified--preventing him from ever finding peace. Hell, it shows in his argument that the qualities of a soul diminish with sundering too. For one, the default quality in a person isn't positive. He frames things in terms of other shards becoming proportionally less intelligent for example, or less kind--but arguably cruelty should have been diminished as well. The civilizations and inhabitants of other shards are also, notably, not at a huge personally/intellectually different framework compared to The Source--where souls are more dense and would (by Hades' argument) have been more advanced and capable.

What we actually know of unsundered versus souls mechanically is that they are more aetherically dense. Being more aetherically dense, it takes more dynamis to influence them. The ancients still feel absolutely and are vulnerable to Meteion, but the sundered are probably a bit more reactive on the whole. It might also be like an inertia situation where once an unsundered starts to feel something it tends to continue and build. That's speculation though.

Zodiark's tempering appears to be closer to magically enforced mental illness in the sense that it warps thought patterns, elevates some tendencies and minimizes/negates others, prevents certain ideas, twists perception, keeps some memories or experiences at the forefront while diminishing or losing others, etc. Psychological wounds that are useful to the mission are kept open artificially well past the point someone would have naturally started to scar over. There is a reason I've been arguing that it's closer to coercion and insanity plea in terms of diminished responsibility. The tempered aren't even able to accurately understand the situations they are in due to thought warping, and claims that their position is reasonable amounts to a completely psychotic person claiming not to be crazy. It's not as simple as mind control from an external source. It's that the person's own thoughts and tendencies are manipulated in unnatural ways to form a cage forcing them into compliance with the primal's mission.

I'd argue it's also very suspect that Elidibus, the lunar shades, and (IIRC) the despairing post-Terminus ancients Venat encountered all separately repeat the exact phrase wishing for 'a world free from sorrow'. Lahabrea explicitly referring to Zodiark as 'the master' at Praetorium strongly indicates tempering too.

A major source of confusion stems from the following scene:

Creation magics are complex and highly sensitive, requiring a tremendous amount of focus. A single moment of distraction can change the outcome of creation. Hades creating his phantom Amaurot having an idle thought 'Hythlodaeus would know the truth' is enough to make the shade of Hythlodaeus aware, even if it wasn't on purpose. Even if it was a split second.

Zodiark was a creation that involved not only the sacrifice of half a star (so likely billions of people)--it also involved the active participation and focus of those people in the summoning process. We know from the environmental storytelling and evidence at Akademia Anyder that I cited in other analysis that Lahabrea was the mind behind the Zodiark concept. We know that the scale of the creation was enormous to the point that it would not function without elevating one individual to steer it--the Heart. This being Elidibus. But the actual summoning was still extremely complex and on a vast scale involving multitudes of people at different skill levels. Hythlodaeus, while experienced as Chief of the Bureau of the Architect, has very limited abilities in creation himself due to aether deficiency. He still sacrificed himself as one of the participants in Zodiark's summoning ritual.

Faith was necessary to simplify the process across that many people of varying life experiences and skill levels. The Convocation would have been handling the more technical elements and forms the concept would take, and guess who was at the head of the Convocation's efforts?

Lahabrea. Who has recently failed to contain Archaeotania despite his people's every faith in him, who we know to be extremely traumatized and has every reason to be terrified not only of the situation but of not performing up to the expectations placed on him. For god's sake, one of the last things Athena said to him involved calling him disappointing after getting full access to his soul.

A single moment of Lahabrea being afraid and hoping everyone would be able to join together to save the star, to be on the same page, would be enough to cause tempering. He's not perfect, but he's been expected to be. He's expected to have perfect composure, impervious to normal human emotions. And of course emotions bled through at a time like that.

The same hope that others would join in to support the mission has bled into every subsequent primal summoning where tempering became a problem.

Venat's summoning technique is different from the summoning technique used by the Ascians. It's also different from the technique used by the Loporrits. Venat used standard creation magic without elevating faith as a tool. She had less people to worry about. The loporrits decided faith would be a useful tool for The Ragnarok insofar as the primals could help fuel its journey, but going off of pure faith rather than the hybrid of faith and strict procedure is dangerous. So they combined the two in a controlled environment knowing the risks.

What Livingway is saying is that using the hybrid technique that is being employed for the first time in that scene, a primal as powerful as Zodiark would cause a slight tug instead of the full force of tempering. Normally there isn't any sense of influence at all with that technique. Zodiark is on a scale and at such a monumental power level that even the safe method would try to influence its summoners along with any bystanders. Zodiark has the most powerful tempering of any primal that has ever existed.

I also want to take a moment to point at what primals are and how they work as distinct from standard creations.

When discussing creations, the shades at Hades' phantom Amaurot mention that souls are gifts from the star and cannot be artificially created. This is part of why Hermes claimed to be so distraught about the way concepts were being handled--there wasn't any accounting for dynamis as a factor.

Livingway mentions that Venat forbade loporrits from making anything possessed of a soul (impossible) or similar.

Here I'm going to point you back to the lecture from the ARR quest What Little Gods Are Made Of:

Primals, brought into being with faith rather than as pure technical concepts, have something like a soul. They are archetypes shared by the living and when they are slain, they aren't destroyed because archetypes can't be destroyed. They return to the aetherial sea, like souls, until they are called forth again. These archetypes reflect common human experiences and desires shared across many, many people. It makes sense that Zodiark would be built off of this premise in the first place as a way of creating common ground with that many participants.

It also makes some sense that something resembling a soul is advantageous, since logistically in FFXIV souls are sources of power in their own right. Thordan, Nidhogg, Shinryu, and The Alexandrians can attest to that.

I understand that there are people who prefer not to use tempering as a key factor in characterization of The Unsundered, and disregard tempering from their headcanons. Obviously this is allowed, but it's not canon. The game is explicit on this point and underlines it multiple times in multiple ways. Hades when told about what lies ahead is completely horrified and does not want to go down the path the Warrior describes--not just for his own sake but because he morally disagrees with it. His line about staying true to his principles at Ultima Thule is deliberately ambiguous--is he referring to pursuit of the Ardor? Trying to save his people? Trying to resist tempering as best he could despite being helpless against it? Giving the Warrior of Light an opportunity to mercy kill him? We don't know.

And regarding the memory of Lahabrea saying he can believe he would get lost trying to save his people to the point of becoming something horrific during Anabaseios... it's very, very important to remember that Lahabrea hates himself. Lahabrea just accepted for years that Erichthonios is better off with the idealized memory of his dead, abusive mother rather than the living father who rescued him. Lahabrea has been ready to commit pseudo-suicide throughout Pandaemonium. His entire Savage transformation design reflects that he thinks the only thing he's good for is being used for his DNA and serving to protect people as Lahabrea. He tries to shield his heart with his wings and the left arm representative of his personal self is long/at a distance, anemic, and basically non-functional due to too many joints. He doesn't want to exist as a person because he hates himself and he expects to be hurt.

And that's before everything to do with The Final Days.

Lahabrea is not a reliable narrator when it comes to questions about whether Lahabrea is a good person. He might be the least reliable source you could find. He is a guilt katamari who is ready to think the worst of himself given the slightest opportunity.

A huge part of what makes Zodiark's tempering interesting is that even if any of the Unsundered are freed, it's difficult to definitively answer the question of whether they might have made the same choices organically. Anything in their heads that might have given them tools to make another choice was taken away. And we know the sundered Convocation members were not tempered when they decided to join The Ardor as Ascians. Fandaniel was able to kill Zodiark because of this.

As it stands though, none of the Unsundered were free. They cannot be judged by the standards of people who are.