Wow, fantastic! I love the way the grandfather is in contact with an alternate culture, or anti-culture, that's threatened by the wizarding world's relentless drive towards normalcy. Very cool -- I loved Fenrir in the HBP, but was a bit worried that he could be too easily treated as a cartoon villain, which would make werewolves less of a moral challenge to the wizarding world social order than they seemed to be in the Remus plot arc. Your werewolves have an ethic of their own, though, however bloodthirsty its values may be. Neat!