Jason laces his hands together above his cup, weighing his words a little before speaking. He doesn't know why exactly he's hesitating. If his words will make Lupin judge him, so be it; the moral opinions of others regarding his acts have long since ceased to matter to him.

Except for those times when the painful earnestness of some upright soul sneaks past his jaded weariness and makes that tiny, battered part of him attempt to be a better man.

"The exertion, yes, that is part of it. In my practice magic.... usually has a cost. Often payable in blood."

One that he often avoids paying himself. He's killed a lot of goats, rabbits, and birds over the years. And the occasional human. Of course, most recently that wasn't an option; the back of his left hand still bears the visible mark where he cauterized his own cut with the hot metal of a knife.