Oh, hey... Hey, now. So-much-yes. I tend to have, shall we say, issues reading any sort of lengthier fics; end up being distracted by other-reading, blahblahblah. But this? Was very much compelled to continue through, hear further details and watch as the characters became so-very-substantial (if anything, this may've distracted from other-reading, hmhm). Quite enjoying your style overall, not to mention the changes in tone offered throughout (and some really-rather-lovely tragic touches, aye).
And the details offered, whether regarding the characters (and each of the ghosts-to-be seemed to hit the stage fully fleshed out... Severus also proved quite the solid presence, and found the dynamics of the initial staff meeting and its participants all kinds of excellent), more historical-type tidbits (the pact that kept Benedict out of Hogwarts, por example), glimpses of magic... So much interest and color added, there (and rather than "added," should probably say something more like "woven in," because the details didn't feel extraneous or distracting, 't'all). Right, and taking us through the experience of becoming a ghost? Most eenteresting touch, shall we say quite captivating in an eerie fashion? Rather a fan of the way you've drawn Severus into connection through his own near-ghost experience, and the alternative offered through him.
Also. Particularly fond of... "Have you ever spoken with a ghost about their life - what honestly happened, not just the caricature of it? They report it as some second-hand tale, with all the exaggeration and vagueness of a picture book. It's not a life-story, it's the imitation of one." Love. Love, love, love. Also, "personality-shard".
Annnd will stop. Apologies for babbling and excessive use of parentheses, but really did enjoy reading, so-o yes. Rock on. :D