Dragon Age: The Missing (Comic Miniseries)

There are definitely hints this could be the case scattered around in all 3 games. Firstly, there is Flemeth/Mythal's plan to capture the soul of the Old God. I feel this is likely because it will weaken her enemies. Otherwise, contrary to what the Grey Warden's believe, them killing the Arch-demon doesn't destroy the soul but liberates it to reunite with its other half, which is currently in the Void. Hence her saying that the soul in Kieran was "snatched from the jaws of darkness". Bear in mind that in order to attract the soul to the embryo, it needs to have an element of the taint within it.

Secondly, there is Merrill's version of the betrayal of Fen'Harel. In her story, Fen'Harel tells the respective gods that he knows the location of a weapon that will win the war. They head off for the location and he closes his trap. This always struck me as curious because the "official" Dalish version says he merely called a truce in the fighting and suggested each side return to base whilst he negotiated between them. Knowing what we now do about his relationship with the Evanuris at the end, the official Dalish version doesn't ring true. However, if we assume that he used an agent to approach the Evanuris, rather than doing so personally, then Merrill's story sounds plausible, particularly since Solas says that if he hadn't imprisoned them, they would have destroyed the entire world. So, let's assume that what they sought was the red lyrium idol. He puts some red lyrium in the Eternal City as bait to draw them in because they can sense it and believe the agent's story is true with the trail pointing to one particular eluvian that leads to the Void. Once they had used it, he springs his trap, sealing off both the red lyrium in the now Black City and the Evanuris in the Void. Exhausted, he then went for a nap thinking that he has all bases covered and leaving his spirit form patrolling the Fade.

Unfortunately, he hadn't anticipated human mages using knowledge they scavenged from elven ruins to get their magic to a level that would allow them to open the Veil. Nor had he factored in that the Evanuris had left an insurance in the form of a dragon with a piece of their soul resting in the Deep Roads. The latter established a new cult dedicated to the Old Gods (who wisely kept their true identity secret) and guided their followers down the years to the point where the assault on the Black City took place. This wasn't sufficient to release the Evanuris but did release the Blight. Many centuries down the line, Solas wakes up and discovers not only that the elves have lost their immortality and innate magic but the catastrophic event he was trying to avert, the release of the Blight, had occurred in his absence. Not only that but a group of adventurers discovered the ancient thaig where he had hidden the idol. Red lyrium, which is even more potent than the normal blight, is spreading. The world is doomed and so he thinks the only possible solution is the destroy the Veil and cleanse the world with pure magic.

This scenario does sort of fit what we know of the Evanuris and Fen'Harel, plus what Corypheus maintained about the Golden City being black when they got there. The reason why it appeared golden to people up until then is because they believed it should be golden and it was only when a group of mortals encountered the reality that then illusion was broken.

One thing I'm not sure about is the idol. Was it really "his idol" or did he just claim it because of what it represented? Also, given what it is capable of doing, it is surprising that Corypheus hadn't heard of it and at least paid a visit to Kirkwall to check out Meredith's statue. Still, apparently the knowledge that it would have reformed within it was something probably only known to Fen'Harel, so this could account for Corypheus' lack of interest in it.