Warning: contains spoilers for DC vs. Vampires: Killers #1!
In the limited series DC vs. Vampires: Killers, Harley Quinn's long-evident plot armor finally gets literal with an awesome new power. As every other living DC hero and villain struggles to stay alive against an army of the undead, Harley's new ability makes her one of the resistance's strongest assets.
DC vs. Vampires has the heroes of the DC universe take on an undead menace, similar to the popular series DCeased. As a vampiric threat begins to pick off the Justice League one-by-one, Batman endeavors to get to the bottom of it, knowing anyone could be turned into a vampire already. After Dick Grayson is surprisingly revealed to be the Vampire King and takes out several members of the Bat-Family from the inside, the heroes are overrun, and the vampires reign supreme. A tie-in entitled DC vs Vampires: Killers #1 sees resistance member Jim Gordon deliver a vial of Lex Luthor's blood, one of the only things able to kill a vampire, to Harley Quinn, now the leader of an underground crime network.
DC vs. Vampires: Killers #1, from Matthew Rosenberg, Mike Bowden and Eduardo Mello, set after the main title's sixth issue, focuses on Harley Quinn and her new role as a crime boss. When Catwoman reveals herself to be a vampire and tries to bite her ex-friend, Harley makes a potentially game-changing reveal: she has injected herself with Lex Luthor's blood. This grants her immunity to vampire infection and actually kills Catwoman when she tries to feed on Harley.
Harley's new ability is a major asset in the resistance's efforts against the vampires, as she now has proof that Lex's blood can take them out. Moreover, it means that she cannot be killed by a vampire bite like the rest of humanity. This invincibility plays on a common trope with Harley in alternate-universe events, as her popularity as a character often means she survives even apocalyptic situations. Harley is currently among the last surviving heroes in the DCeased universe, staying by the side of her partner Ivy while she guards the Green. Incredibly, Harley also manages to be one of the last heroes standing in the Injustice universe, despite having played a major part in Superman's turn towards darkness. On the cinematic side of things, Harley is the only active member to survive both Suicide Squad films, once again proving her durability in deadly situations.
Harley's survival rate has become a running joke among fans of these alternate-universe stories, and DC vs. Vampires: Killers #1 carries on the trend by giving her a power that literally makes her immune to the central threat. By injecting herself with Lex Luthor's cure, Harley Quinn has codified her usual plot armor as an actual ability, surviving in a world where even Batman and Superman couldn't last.
DC vs. Vampires: Killers #1 is now available from DC Comics