Such an excellent imagining of Fenrir. You've done exactly what you set out to do: made him understandable and complex without excusing him. I like the tone you've created for him: wry and ironic and bitter and so chillingly matter-of-fact. Lupin is strongly characterized, too -- very IC. I like the way you set everything in political context; the racial and class dimensions are very effective.
Just a few of the great lines:
even without the moon I could follow their scent. The man stank of self-righteousness and privilege
The shed of a man who meant to keep what was his.
"One must take proper care of one’s prized possessions." John Lupin patted his son on the head and proceeded to ignore his own advice. Oww.
Lad, you’ll go everywhere with a werewolf for the rest of your life
It was like watching water tumble down a rapid, so fluid, and so powerful
as far as I was concerned the only proper wizard was one with his throat torn out. Or one that paid. The essence of your Fenrir
I thought that my life would never get better than this. That time I was right. Very painful.
The wolf was all that I had left now, and so I fed it.