I love a good mystery, and this was very well done as a mystery, with Harry's searching for answers and all the wandlore, which made *sense*.
It's also so rare to find bdsm done WELL, but you accomplished that here, giving brilliant insights to the sub's state of mind. I wasn't sure whether to be squicked or not by Snape's presence, but you handled him well, keeping him just enough in the scene to keep control for the wandlore, but not overly so. (so that we could enjoy the Harry/Draco.
And it was unbelievably hot. Definitely going in my favorites. *g*
((ha ha, and LOVED the reference to Dumbledore in purple!))