He folds his arms in as if fearing leaving them too loose will invite a pricked finger or other manual check.

"Whatever a blood drive is, I want no part of it. 'Type O' means nothing to me, and we're different species, so how is our blood supposed to be compatible?" He may be edging his feet back, slow but steady, toward the door. "I'm a troll. We both might have horns, but I sure as fuck don't have wings, and if I did they wouldn't look like that. I'm not even a mammal, and I can promise already that humans aren't going to benefit from me."