Are you not worried that I'll cast some magic or try to make you like me?

[Not that he could do the former or would attempt the latter, but he would certainly think anyone who had an inkling of what he was might be more... cautious about making such an offer. Particularly from a man who'd already died.]

To answer your question, blood is blood. I've... teeth that appear that make it easier to draw, or it can be consumed from anything. There's no significance to the vessel, other than what it holds. But it's not an offer you have to make, Jon.