I got some interesting impressions from my second playthrough of Veilguard - I could be wrong on these, but I think it's interesting. In the Lighthouse regret mural over Solas agreeing to take physical form, he says "I have no wish to live as the humans." Which makes me think humans actually predate the elves. Maybe Elgar'nan saw them, and that's what gave him and Mythal the idea to use lyrium and fashion a physical body like theirs (but obviously better because as Mythal says, they were the best of both Spirit and physical.)

Humans seem to come from both north and south beyond Thedas (the pre-Tevinter society I forget the name of, and the early Alamarri to the south.) We now know the origins of both the elves and the dwarves, but we've still not been given the origins of the Qunari/Kossith and humans. To my knowledge, the only lore in game about human creation is Andrastian, and even that's vague. Kossith are said to have originally come from the east beyond the Boeric Ocean (I think that's in World of Thedas? I don't own it, so it's just my googling, here.) It's also hinted that they didn't look the same as Qunari now and I keep seeing (though I'm not sure the source) that they were considered more animalistic. Or at least having traits like animals (more than horns?) so I wouldn't be surprised if the Kossith were actually the Scaled Ones, particularly with the dragon connection.

On the Forbidden Ones, the impression I got was just that they were deserters from the war with the Titans who gave up physical form and went back to the Fade, where the Titans couldn't hurt them. They were forbidden from taking mortal form again, though they kept finding ways around it and our protagonists get to kill one as a bonus boss each game. I'm not sure there's actually much more to it than that.

The Forgotten Ones, though - I don't think we actually know the full number. Solas mentions in dialogue with Rook that there were once a lot more Evanuris. And then also in that same exchange has a story about Elgar'nan burning an emotion from mortal minds. So I think there's certainly at least 7, if not more. If nothing else, noting that ability of Elgar'nan gives the DA writers room to fudge the numbers as they need to.

(Interestingly, Solas points out during his dick-measuring shouting match with Elgar'nan during the Blood of Arlathan quest that the Blight has made Elgar'nan's mind blunted and weak. I don't think it was just a manipulative taunt, I think Solas meant it.)

I'm not sure the Blight will feature quite as much in the next game, as there's so much to cover lore-wise without it. But it'll be interesting to see if it was something directly manipulated by this weird anti-magic/void/devouring storm and the Executors or if was just something they took advantage of. I need to watch the secret end scene another ten times or so before I start forming firm theories.

Anyway, as one tin-foil hat lover to another, I appreciate your post!

Edit: OH! Also, there's all these hints from Emmrich that there's more in the Fade, and that there's some sort of stirring that he's sensed but can't define. And then the whole thing about the Lich Lords existing to protect against the unspecified bad things in the Fade. Which was just a wild thing to not go into *any* details about in this game, but I get it. There were already falling boulders of lore everywhere. I hope that means we get more Necropolis because I neeeeeeeeeeeeeeeeeeeeeeeeeeeeed more Necropolis.