He's read stories about vampires - mostly the work of P.H. Jonesworth, who supposedly even met Count Strahd of Barovia - so between the sharp teeth that catch his eye and the joke (joke?) about his blood type it's enough to make him think. Wonder despite being advised against wondering.

Ezra would probably like this man. He's very into vampires.

"Right, my name." He considers whether or not he should give a fake name, but if this man is a member of Riftwatch then it would probably be best to be honest. Holding out a hand towards Astarion to shake, he says, "Allumin. Blood type: edible."