This was a wonderful conclusion to the story! I read chapters 1 and 2 when you first posted, but held off on 3 and 4 until I finished reading the first volume of the Phoenix Wright manga, which really helped me to enjoy the story more, although it was easy enough to follow even without knowing the PW storyline.
It was a nice touch, having Maya channel Dumbledore, and it was an absolute stroke of brilliance to have Alecto be Meg Erinyes! It's so obvious in hindsight once Snape explains it; at least for someone who spent quite a bit of time studying the Greek tragedies in college. I'm kicking myself now for not figuring it out earlier.
I also loved Tonks and cracked up at her description of Alecto as a "batshit insane wanker"! ^_^
Thanks for sharing--it was a wonderful mystery story, and I enjoyed the Phoenix Wright crossover!