The following article contains spoilers from DC vs. Vampires: All Out War #1, on sale now from DC Comics.
To say that things are dire for humanity in the wake of Nightwing's new world order is an understatement. Most of the world's heroes are dead, the human population is being herded into camps, and the surviving heroes are on the run. DC vs. Vampires: All Out War #1 (by Alex Paknadel, Matthew Rosenberg, Pasqualle Qualano, Nicola Right, Troy Peteri) struck another blow by destroying one humanity's last safe havens.
Nightlight was not only a place where people could be safe, but also one of the last ways for the world to produce food after the vampires shrouded the world in an endless night. Captain Atom was the key to this, fueling the farms with converted solar energy. However, the vampires managed to infiltrate the base and force him to detonate, triggering a nuclear explosion, and inadvertantly mirroring the ending of the iconic Kingdom Come story (by Mark Waid, Alex Ross, Todd Klein).
As one of the few heroes capable of utilizing solar energy, Captain Atom was too valuable to use in combat, instead choosing to use his gifts to provide humans with a source of energy to grow crops as well as a proper day and night cycle to ensure that humans get a daily dose of needed vitamins. While that last one may sound trivial in comparison to food production, a lack of sunlight can lead to people becoming more susceptible to chronic diseases. Captain Atom may not have fought vampires but he fulfilled a vital role for humanity.
The vampires knew this though and they seized the first opportunity to be rid of him. Using Damage's explosive abilities, they forced Captain Atom to detonate, in the process depriving humanity of a major chunk of their food production. However, the immediate consequences are a more pressing concern. The exact range of the blast hasn't been established yet, but given Captain Atom's pleas not to be detonated it's likely the explosion will completely destroy Nightlight.
This mirrors what happened in the final battle of Kingdom Come. The heroes and villains engaged in one last battle that would have decimated the planet. The United Nations authorized the use of nuclear warheads against them, resulting in a cataclysmic explosion that killed a good portion of the world's metahuman population. Now it seems that another Elseworld's story seeks to repeat this level of devastation. Only this time, it is the survivors who are being destroyed.
Yet, from the ashes might come hope. The survivors in Kingdom Come rallied in the aftermath and managed to help build a better world. It's possible that some heroes and villains might survive the explosion triggered by the vampires. Though whether they will be able to do the same thing is questionable. The world they knew is gone, there is no structure to integrate into or even work with really. Most of the rebels can't even agree on a course of action against the vampires. While Nightlight isn't the last living stronghold, it is a devastating blow to what little hope is left on Earth.