So, in the time of Elhvenan, the veil was already old. Very old. Before the Elvhen gods had been other, older beings. The Titans? The Forgotten Ones? Could those have been one and the same? But, at some point they got corrupted and possibly sealed themselves away in the Void to save thedas, erecting the first Veil in doing so and giving rise to the first corporal beings. The Ehlven were immortal and possibly as much spirit as living beings, so connected they were to the Fade and it’s magic. even then, some longed for the time of old, before the Veil came up (could they remember it? Possibly). Amongst them some rised as gods (were they more than very powerful ehlven, I can’t really be sure). El’garnan, Mythal, Anduil, June, Sylaise, Falon’din, Dirthamen, Gilan’nain, Fen’Harel (might be forgetting one or two, if so I’m sorry).
Amongst them, it seems Fen’Harel might have had the most connection to the gods of before (could he have been possessed of the spirit of one of the older gods, the way Flemmeth is with Mythal?), and understand the dangers of the Void. Anduil, always the huntress, on the other hand, didn’t. she went there to hunt, and fdouns something there that should have stayed there. My guess is it has to do with the taint and red lyrium. and she brought it back everytime she returned. Every time a little madder, until Mythal had to fight and possibly turn her tranquil (I like that theory). But, I believe it was already too late. The taint spread amongst the gods, slowly rendering them insane, the way the taint and red lyrium do. Falon’din bloodied in his temple is only one example of this. It got so bad (maybe after they killed Mythal?) that Fen’harel finally realized there could only be one solution. Seal his fellow gods away before the taint spread wider and Thedas was destroyed (could the darkspawn actually be elves and other beings corrupted with the ehlven gods and driven underground to search for the source of that song they all hear?). How he managed that, I’m uncertain, but I think it has to do with a very special eluvian (sleeping behind the mirror), and strenghtening the veil the ancients (titans?) had created. Which would explain why the veil feels older in some place than in others. The spell took such power however that he had to go into uthenera afterward.
But, as his quest with the artefacts shows, the veil is thinning again. That in combination with red lyrium appearing everywhere in greater and greater quantity tells me his solution was only temporary and we’re coming to a moment where the veil won’t hold anymore. The young, elvhen god are probably quite mad from the taint by now, and we also have some older gods from the void (do they even still live/exist?).
I know this theory probably isn’t the right one, but I needed to put it out there and welcome any addition/correction to it. I haven’t touched the old gods of Tevinter as I’m not sure how they are worked into this. I just feel strongly that the elhven gods might not have been the first gods, and the veil probably precede them. I also feel like it’s threatening to disintegrate and that if this was to happen, it would be… really bad. Perhaps that is the task Solas feels he has to do along. preventing it, and not bringing down the veil himself and some have theorized.