It was a particular piece of TG fiction over at Sapphire's Place I once read. At least I think it was at Sapphire's Place...

I vaguely remember the premise, something about magic and the character grew younger as when they transformed (male to female, of course, because tropes always win out), I think? But the detail I remember is that the main character had a teacher that was an ancient evil man that got turned female (and something about sexuality?) by the powers that be a long time ago as a punishment but the main character convinced the powers that be that just punishing them for so long without a chance of redemption was bad? And the formerly evil wizard person was super grateful or something?

I know its super vague, but I just remember that plot point. A side character might have been a cop?

I honestly don't know where to ask for this type of thing.