Great concept, thrilling story; I'd very much like to see what happens next (hard to predict as there seem to be no clues as to the secret society's exact agenda). I think I've caught the epithet 'chilling' floating about the comments - that's exactly right. Political struggle, extreme discrimination and dictatorship turned on its head in HP verse is a recipe for a delicious story, effectively exploited here.
Finnegan seems somewhat too powerful and his followers too radically stupid, but, I guess, that goes to underscoring the point of the story in the limited lengh of the text.
One thing that fell out of the narrative, for me: explicit sex. Had nothing whatsoever to do with the plot, being therefore mindlessly gratuitous to the point of disturbing the pacing and distracting from the story's intent.
Special thanks for the skeletal phoenix as a symbol of the resistance.