no one HAS so let's freaking outline this sucker. first we need to look at What Needs Fixing, which is cain's insane circular logic that has him thinking that he's disposable, and that being disposable is a good thing to aspire to. it's the fact that he thinks this is a Good Thing that is what mostly needs to get fixed; it's very difficult to break people out of unhealthy mindsets that they're dead certain are Good. like, with a lot of depression-based mindsets you think stuff that's terribly unhealthy about yourself but you Know it's not good, right? cain isn't like that at all, he genuinely thinks that all the terrible things he thinks about himself are not only Good but Necessary. and there's nothing more dangerous than a zealot, as they say

so! cain's already been through one life-shattering event (owen stealing his eyeball, but actually specifically owen outing him as a wizard is what did more to him than just...owen taking his eye) and because he is a deranged person, he is grateful to owen for completely upending the life that he'd very carefully built for himself over the course of his entire life. this is because cain knew that constantly lying about himself was a Bad Thing To Do, and now that he doesn't have to do that anymore, he can live a freer life, more true to the principles that he stakes his identity on.

breaking apart the aspects that he considers Good is going to be SIGNIFICANTLY more difficult than just ripping his eye out. it needs to be something that is not only life-shattering, but also completely his fault. he can't have anyone but himself and his twisted-up ideals to blame for it. the incident with owen happened because of owen's nature as a northern wizard and because of his mother's insistence he lies about himself, two things that ultimately have nothing to do with cain himself.

which is why i think cain needs to finish slipping down into his darkest impulses, the ones where he ignores his morals and what the people he love would realistically want him to do so that he can do what He thinks is Right for Them. what i'm saying is that putting arthur or owen in a cage and then that OBVIOUSLY blowing up in his face could fix him

...and it would specifically fix him because arthur and owen will hopefully still want to love and care about him even after it getting shoved in their faces how unstable cain actually is. owen has already mostly crossed this bridge--in the whereabouts of the left eye, when faced with the idea of cain being less than ideal, owen almost ripped cain's eye back out, but in ms2 when faced with the reality of cain being less than ideal, he immediately went off to find arthur to get cain back on track. arthur...is still not quite there, but if he can navigate oz being the world's worst war criminal then surely he can also deal with cain putting him in a cage. right. right