Scene of the crime.
Caine, first child of Adam and Eve, was cursed by God for killing his brother Abel. Vampires believe that he was the progenitor of their race and the father of the antediluvians. He created the first city, Enoch, and may have been the first creature in history to hold the Orb.
Whether or not he actually existed is up for debate, since he did not appear at Gehenna, but it is a part of vampire lore.