The following contains spoilers for DC vs. Vampires #7, now on sale from DC Comics.
Throughout the course of DC vs. Vampires, the heroes and villains of the world have been the targets of a twisted conspiracy that resulted in humanity being dethroned as Earth's dominant species, with many of its most dangerous figures either being wiped out or corrupted.
DC vs. Vampires #7 (by James Tynion IV, Matthew Rosenberg, Otto Schmidt, and Tom Napolitano) reveals just how dark things have gotten for this version of the DC Universe and confirms which heroes remain, as well as which one is potentially the ultimate weapon against the undead.
As revealed in the opening pages of DC vs. Vampires, the vampiric horde have corrupted numerous DC heroes and villains, with Superman, Shazam, Aquaman, Hawkman, Firestorm, Blue Beetle, and Bulleteer being among those turned. Numerous others are confirmed to have been killed, including Superboy, who was ripped apart by Wonder Woman and Shazam. Serving at the behest of the Vampire King Nightwing, the vampires have spread their influence across the globe as a small band of survivors struggle to make their way to a rumored safe-house. The mission comes at the cost of numerous casualties, including Adam Strange, Killer Frost, Peacemaker, Wild Dog, and Director Bones.
Meanwhile, Raven is bitten and potentially corrupted, but she may have died before being fully turned. Luckily, Firestorm explodes after being killed by Jayna -- hurting the vampires enough for Director Bones to help the lone Wonder Twin find the location of Kandor which has been converted into the final base for the last of the uninfected heroes and villains. The biggest advantage the heroes gain though the encounter is the revelation that the last mission was to try and save Supergirl, who remains uninfected but weakened by the now sunless world.
Supergirl's presence as a secret weapon may, in theory, be seen as a real boon for the heroes. Their current base inside the remains of Kandor means Supergirl's Kryptonian knowledge might be able to help utilize the city's defenses for their fight against the vampires. They even have a plan to travel across the world, undo some of the damage to the planet, and return sunlight to the world, which would give them a much needed edge over the undead.
However, there's always the chance that Supergirl's strength as a potential counter to the deadliest members of the vampire nation could backfire. The Last Surviving Kryptonian is heralded as a "symbol" that could help turn the tide against the undead bloodsuckers and inspire resistance. But this also means that her death (or even worse, her own corruption into a vampire) could be the final straw for the shattered remnants of humanity. Supergirl will be going up against a lot of powerhouses beyond just Superman, and her innate weakness to magic might be an easy way for Nightwing and his forces to take her down before she is able to turn the tide. Regardless, Supergirl remains the survivor's best option, and this in turn speaks to the grave circumstances facing this horrifying world.