Former Territories of the Evanuris

Solas regarded them as essentially the enemy, so he is hardly likely to go into detail of which were more culpable than the others. It is entirely possible that by the end they were totally corrupt by the desire for power, particularly if red lyrium was floating around since we know that can accentuate bad traits in people. It is also likely that when someone was threatening their collective hold on power, they would naturally close ranks and likely put aside their differences in face of that threat. That does not necessarily mean they were all as bad as one another or that they all knew what the others were doing.

Solas says that Mythal was the best of them and that she cared about her people. Was that possibly rose-tinted spectacles on his part? Clearly, whilst she reprimanded and dealt with individual Evanuris if they got too out of hand, she seemed happy to preserve the status quo. Whilst we know that she was murdered, the don't know exactly why. There are some theories that she actually backed Fen'Harel's rebellion in secret and when the others discovered this, that is when they killed her but they are only theories and our words to Solas, combined with his answer, suggest he only rebelled against their rule after her death.

Why do you think Dirthamen is least likely to be implicated? If anything, I would think he was the one who helped engineer it. Mythal was acknowledged as having power and authority over the other gods, with the possible exception of Elgar'nan. Would it be any easier to catch her off guard than it would Solas without some sort of trickery? Who better to keep a conspiracy hidden until the last moment than the god of secrets? Also, it might be difficult to keep a conspiracy hidden from him, so if the other Evanuris were plotting something, he would know about it. Given what his priesthood did in his Temple, first high priest to preserve his secrets and then the others in retribution for his actions, it seems Dirthamen was not a good influence on them. Lastly, there is the connection between him and Falon'Din.

I am prepared to believe Solas' words about the latter, since they seem confirmed by what we discover in the Vir Dirthara, that he was constantly stirring up trouble, plus the inscription in the Temple of Mythal makes him sound pretty sinister. He was likely the first necromancer and is clearly associated with death/the dead. However, if the elves were immortal, that means he could not rely on people dying a natural death to obtain his subjects, so hardly surprising that he was constantly urging violence. His followers also call him a "master scryer" and ask for his guidance "through shapeless worlds and airless skies". That is clearly referring to the Fade and the Dalish associate him with guiding those in Uthenera in ancient times, along with Dirthamen, where the elders would discover the "secrets of dreams". However, we also know that in ancient Tevinter the Dreamers could seek out their enemies through the Fade and kill them in their sleep, so maybe Falon'Din/Dirthamen operated as a sort of secret police, with their followers acting as their operatives. As I say with regard to Dirthamen, if another god wanted to keep something hidden from prying eyes, who better to go to than these two?

So, I can fully imagine a conspiracy between Andruil, Ghilan'main, Falon'Din and Dirthamen but I think the main motivator was Elgar'nan. There is a mosaic that we can discover that is referred to as the Arch-demon. It is assumed that it shows this and was made by Tevinter artisans, but Gatsi says, in connection with one of the others, Freed are the Slaves, that it looks as though the Vints altered an earlier work. They were known to do this with elven artifacts, claiming them for their own. So, I wondered if the Arch-demon was in fact depicting the conspiracy against Mythal, shown as a dragon. In which case, there are 7 Evanuris shown but Gatsi interprets various lines of sight from 3 dragon heads. Two are turned away from lines that piece the dragon, so seem to be doing the damage, but the third head is looking directly at the one who appeared to miss but clearly the dragon knew was the instigator. "She was betrayed as I was betrayed" (by her husband). So, if it does depict her death, two (likely Andruil and Ghilan'nain or Falon'Din) were responsible for the fatal blow, Dirthamen tried to shield the conspirators from her knowledge but she knew who had actually ordered it.

Incidentally, Elgar'nan would seem to have been ackowledged by all, including Mythal, as pre-eminent among the gods and was clearly someone you would not wish to cross, seeing as even the Dalish know him as the spirit of vengeance. So, if he decided that Mythal should go, would any of the others oppose him? Now knowing about the threat but not warning Mythal or trying to prevent it, still makes them guilty of her death, but their crime could be more one of cowardice or simple self-interest rather than actual malevolence towards her.