According to another codex mending veil tears is one of the hardest feats of magic which is deemed impossible without blood magic or help of a fade entity.
And yet you think one elf mage created the entire Veil?
Also the veil is "vibrations" of magic so in a way it doesn't actually exist. If that codex is true, that means there are gateways between this world and the fade, Solas closed these gateways. Its not a far fetched idea because existence of gateways between worlds is actually logical.
The Veil exists as whatever it is, a magical vibration, an idea, whatever. There don't need to be gateways in the sense that an eluvian is an object that acts as a gateway. The Breach itself was a type of gap or portal. The mark, Solas' magic, mended that gap. The original gaps were likely cleaner, more defined. Perhaps less obvious, or showing no visible manifestation. Maybe it was just a case where you crossed an invisible threshold and the real world suddenly got more real.
Thanks for considering the theory though.
I don't think that that necessarily means there are any gateways to begin with. If the world was mixed with the Fade, then surely there wouldn't be a need for portals or gateways at all. Thus, there would be nothing for Solas to close.
That's the debate however. Was the world mixed with Fade and Real, or was there a Veil over some parts of the world but not others? Vivienne points out that if there was a time when there was no Veil, human history would have recorded such an existence. It's possible that the Veil existed, but with gaps. The elvhen built their cities inside the gaps as well as in the Crossroads. The humans however existed in the Real where the Veil blocked the Fade. Then after the gaps were closed by Solas, the humans were able to migrate to Thedas.
I would imagine that elven mages of that age would be able to traverse the deeper portions of the Fade without a need for a stable or stationary portal.
According to elven lore as well as some codices in the Vir Dirthara, only Falon'Din and a few others could traverse the deeper portions of the Fade. The Forbidden Ones are said to have abandoned physical form in order to flee to the Fade where the Earth could not reach. Dirthamen's lore states he bound two demons Fear and Deceit to take him through the Fade to Falon'Din.
The area most elvhen likely existed in was the Crossroads. Anyone can exist there, at least a while. But the Fade was reserved for spirits or very powerful mages like Falon'Din and probably Mythal and Elgarnan, and probably the old gods as well.
I don't necessarily believe that codex, since its just one elf experiencing things. Just thinking that its not impossible.
The things we learned about ancient Elves rather shows that the fade was literal part of their world, so the existence of gateways and portals seems unlikely.
Another codex strongly suggests that even in the time before the fall there was a clear distinction between the Fade, the Crossroads, and the Real.
The spirits refers to the unchanging world and its laws. So clearly there was Fade and Real, and the Crossroads was a mixing of both.
This refers to the Fade touching the lands of the evanuris. This likely refers to the Crossroads. Also, there is a deeper part of the Fade that the Forbidden Ones fled to by casting aside physical form. But they also had knowledge of "shape", which lets them travel the paths unaided. This could mean the paths in the Crossroads or maybe the islands in the Fade.
As for how the world existed, the Chant of Light even says there was a time when there was only the Fade. Then the Maker extracted energy from the Fade and made the real world, then he created the Veil to separate the two. He also allowed the spirits to see the real so they could learn, and also for mortals to dream and return to the Fade to have new ideas. But the Chant does not say exactly how the Veil operated. Perhaps the Veil was created with gaps so that spirits and mortals could interact within the Crossroads.