I actually have an alternative "catastrophic" world state ...
So basically my thoughts behind these two (when DAI is out, three) characters is, that they're the three Chaos Brothers.
Even though they weren't born into the same family, they share the same chaotic characteristics ... and they even look alike.
For starters, they ARE mages and they ARE Blood-Mages, which is very important not to forget, so everything they do and everything the third brother will do in Inquisition is about POWER and BLOOD. I decided to give them names of "catholic importance" like Bishop and Cardinal, just for fun, since they hate the Chantry and everything related to it.
Bishop was a Circle mage, he never wanted to bow down - and he never actually did - to the Templars or to Irving.
He betrayed Jowan because he didn't really care ... but in the end he did side with the Circle, because he still had the decency to acknowledge, that a lot of the mages are NOT in the Circle because of their free will ... so he actually plans (planned?) on freeing them, what he somewhat accomplished by pleading for their independence before King Alistair Theirin.
He was pleased with Morringan's plan (the Dark Ritual) and was happy to conceive the OGB, since it would be the first of its kind. Later he actually went with her through the Eluvian, just in order to find his child and kill Morrigan ... because she kidnapped his son, you know?
Bishop actually poisoned the Ashes, he didn't like Andraste anyway. Destroying one of the most important things to the Chantry filled him with joy.
Even though he did not agree with Bhelen on his agenda (Bishop is a straight-forward guy, either you do or you don't is his motto), he did make him king and even gave him the Anvil, in order to get these powerful golems to the battlefield. PLUS - he would have the support of the whole Dwarven Kingdom and the Dwarven King himself! Doing this, he also ensured, that Orzammar can become a hotspot for apostates and maleficar ...
I think you already know where this is going, my Warden was very power-hungry and never bailed on anything, that could make him more powerful (Avernus, etc... ). I think he even let the Architect die, just because he was interested in his research. Oh! And he did not destroy the ancient spirit in the Elven Ruins, after it gave him the knowledge of the Arcane Warriors! Maybe that should be an option in the Keep too 