one thing that does still bug me, is like. what was the great seal before Makoto took over being it and how exactly did the kirijo groups shadow-Persona experiments lead to like, the Death shadow and the pieces of the seal being split into the fullmoon shadows? did the P3 club book go over that? or do you have your own thoughts on it?
What the Kirijo Group did was the following: They gathered a large number of Shadows from somewhere and brought them together in an environment where they could fuse together. When enough of them had fused, they created Death. However, Yukari’s father, when in-between, trying to interrupt the fusion, hence creating 13 smaller Shadows that were incredibly drawn to each other instead. Aigis sealed one of these Shadows into Makoto’s psyche, thus probably giving him an incredible amount of mental energy for a human. My theory is that this might be part of the reason why he was such a powerful Persona User right from the start; even after Pharos separated from him, they were connected by their Social Link by then, meaning that Makoto could still draw from his strength.
What follows now is partly directly from the P3 Club Book, partly my own interpretation of the book and the events of the game. I am going to put the parts that are *not* definitely canon in italics, in order to clarify it:
There wasn’t a “great seal” before Makoto became it; originally something else kept Nyx from recovering and drawing all Shadows out of people’s souls to restore her full being and leave: The survival-instincts of all living beings.
Basically, as long as enough living beings actually enjoy life wholeheartedly and want to continue living enough to either suppress the fear of death or to be able to face it bravely, those thoughts and emotions kept their individual psyches stable, meaning their Shadows wouldn’t even try to escape; A person with an emotionally stable psyche, does not give their Shadow any reason to attempt and break free, not even during the Dark Hour. Deities and Demons originally existed to ensure this system would remain stable; they managed the Collective Unconscious by keeping balance between humanity’s collective fears and hopes internally, while humanity’s religious believes in them on the outside kept the deities and demons themselves powerful and stable enough to go on like that. However, when humanity’s believes change too much… Well, you’ve seen how corrupted Izanami had become by the time Persona 4 happens. And sadly, there’s a real chance Marie will become corrupted as well sooner or later, unless something changes.
The Kirijo Group definitely played a part, but really, they only sped up the process by a couple of decades, at best. By forcibly gathering and fusing Shadows together to trigger the Dark Hour (Because apparently, a powerful enough Shadow is what is needed to create the Dark Hour, and the Dark Hour is what is needed to draw out even more people’s Shadows, one by one, to eventually trigger the Fall), they certainly made the Fall happen a lot faster than it should have, but the P3 Club Book also makes it clear that, with the Collective Unconscious deteriorating as it was, it would have happened anyway sooner or later.
The whole reason the Fall could even happen by the time Persona 3 happened, was because humanity’s collective will to live had deteriorated so badly during the industrial age, that it had birthed a Demon that was powerful enough to actually facilitate it: Erebus. And unlike Nyarlathotep, Erebus did not have a counterpart to keep him in check and balance him out. The collective emotional instability of humans during the late 20th century allowed their Shadows to exercise more control over them; these feelings birthed Erebus, whose mere existence must have made it easier for Shadows to escape, and the more Shadows escaped, the more the collective unconscious deteriorated, making Erebus even more powerful and creating a vicious cycle. It’s like Pharos said: Because the collective of humanity itself has become so seemingly “tired” of life in the recent couple of hundreds of years, the Collective Unconscious has deteriorated to the point that a Demon that should never have been born was born; a demon that can actually command Shadows to abandon their hosts and return to Nyx, all at once, at any time it pleases, if it comes into contact with Nyx’ core.
(This part is entirely my own interpretation:
Personally, I don’t think it’s a coincidence that Erebus was apparently born right after Nyarlathotep was destroyed; Just because Nyarly was destroyed, it doesn’t mean the ideals that created him vanished; he himself said so. So I think that a lot of the malevolence from Nyarlathotep went into the creation of Erebus, kickstarting him into existence, meaning Tatsuya&Co only delayed the inevitable, just like SEES did years later. Basically, all Persona Games since P2 have been about desperately finding “work-arounds” for the deteriorating state of the Collective Unconscious to delay the end of the world further and further, until a permanent solution can be found. So far, we’ve killed several powerful demons and corrupted gods, ruined at least one alternate timeline, sacrificed the existence of THE most powerful god that we had rooting for humanity and turned the possibly most powerful Persona User to ever live into a glorified doorstopper. I wonder how much longer we can keep going like this.)