Started yet another Dragon Age II playthrough with my main Hawke this week, as one does, and hooo boy the Tranquility quest is even more messed up than I remembered it.
Even aside from the nauseating "better to be dead than disabled" vibes, Anders insists there is no option other than to kill Karl because there's no cure... while witnessing that Karl has in fact been (temporarily) cured. Karl is standing there very clearly aware and *feeling emotions* and Anders is like "nope, gotta murder my boyfriend. It's the only answer!"
Like... Why not take him with you and explore why he woke up? You're a healer!
And as a spirit healer who's possessed by a demon, Anders might have discovered he's well equipped to experiment with that. Imagine the justice he could have achieved if he had put energy into curing Tranquil instead of blowing up innocents and plunging all mages into a war they didn't chose.
I also think it's interesting that tranquil mages in Kirkwall aren't just tranquil, some seem to be indoctrinated too. Karl was agreeing with the templars, voicing the opinion that Anders should be made tranquil. I guess he could have just been parroting what they told him, without being able to use critical thinking to question it, but I wonder if there's more to it. Is there additional mind-controlling magic being used in the tranquility ritual in Kirkwall? I wouldn't put it past them, honestly.
