There does not seem to be a plausable lie that could fool the Vampire Lords, so you resolve to tell the truth.
"There is an old legend of such a man," one of the Vampire Lords says. "A man of great wisdom, who cannot die. Everytime he is killed, he reappears somewhere else. I wonder, could this be the man you met?"
"Don't tell me you believe those children's tales!" Draco scoffs. "Those stories have been told from since before any of us, or even our sires, were here!"
"Still," the first Lord continues, "who else could it be? He fits the description, and now Vincent has this strange blood in him which none of us recongizes. None of us have ever met this man, so it remains the best hypothesis."
After a breif discussion, most of the Vampire Lords agree.
Xia states what all the Vampire Lords are thinking: "Now the only question is what to do with him."