Part 2 of my squee
I loved Rufus's "Hard enough for you?" because the sick scum deserved that, for so many things, not the least of which was trying to play on Rufus's desire to make the interrogation go better for him, or at least that's how I read that.
And then I was forced to look at human cruelty and realize that even the good guys go too far, which was just masterful; one instant I was cheering over him getting strangled, and then feeling incredibly sick over Azkaban, because no one deserves that; no one. I love the fact that Rufus performs a surreptitious lubrication charm because there are just some things that are over the top. Your descriptions of the cold and dark were phenomenal; I can't imagine having to live with that, day after day and cling somehow to my humanity. And yeah, Rookwood is exposed as the monster he is, but there's something deeply pitiable about seeing a formerly charming brilliant man cowering like a dog away from his former lover.
And then you bring it all full circle, making us feel contempt for Rookwood all over again as he both refuses to look away or stop this.
This fic illustrates so incredibly well that sometimes, the only difference between the good guys and the bad guys isn't methodology, but morality. And your Rufus has it in spades, fighting for what he holds dear to the very last instant.
And speaking of Rufus, I love seeing the glimpses of why he would make such a good/steady/reassuring Head Auror. And the logic, and the analyzing, and the holding to dignity, even through pain. I loved how much he analyzed and tried to gain the best outcome from a hopeless situation, not for himself but the people around him. And the fact that you had him unable to remain completely stowic through torture and yet cling to his integrity by not begging was just... incredible; your entire spare descriptions of the torture were awesome, with just enough detail to make us understand its horror without feeling overwhelmed with gore.
Mystery author, I can not wait until reveals so I can stalk you madly.