I'm so sorry I'm so late commenting, but I totally missed my name scanning new submissions and only just discovered it while going back over the weekly round-up. I am a horrible person.
Anyway, I really, thoroughly enjoyed reading this. Karkaroff doesn't get a hell of a lot of thought, and even when he does it generally doesn't involve giving him depth, which is exactly what you've added here. It's a brief snapshot, but it's raw and real and he's a three-dimensional, full being rather than an acessory holding up other characters. Good language and flow, and I particularly enjoyed poor Fredya being terrified into submission over the Dark Mark. Poor thing probably doesn't know what it means.