This story was utterly fascinating. I wasn't sure about the pairings, but once I'd started reading, I couldn't stop.
The pain of the ghosts, their very real injuries taken from the battle was such a unique idea to hang a story on, and you executed on it beautifully. The story you elaborated upon for the Grey Lady and the Bloody Baron was very good, but the one you created for the Friar and Nearly Headless Nick was the highlight for me.
Poor Hogwarts, without her house ghosts, at least for now, but I'm so happy that Snape has no desire to become one.