Joker is a vampire in the vampire apocalypse. But, unlike the fallen heroes, he didn't have much of a soul to corrupt in the first place. He's much the same, just with a thirst for blood. The Harlequin of Hate is your not so friendly neighborhood clown, here to keep his darling nemesis on his toes, killing anyone as part of his twisted joke. He doesn't want his everlasting dance with batsy to end, so he will not kill or reveal Batman's identity. 