WARNING: The following contains spoilers for Justice League #36 by Scott Snyder, Francis Manapul, Howard Porter, Hi-Fi and Tom Napolitano, on sale now.
At the start of writer Scott Snyder's run on Justice League, the resurgent team revamped its iconic headquarters in the Hall of Justice, with each of the core members having quarters reflecting his or her sensibilities. However, with the overall facility designed and funded by Bruce Wayne, the Dark Knight loaded the building with plenty of secrets to help the more clandestine elements of the team's mission, largely unknown to his teammates.
Previously, Batman was revealed to have constructed a remote Batcave beneath the Hall of Justice in Washington, D.C., to continue his obsessive endeavors when away from Gotham City. That Batcave also possessed a secret prison that housed the Batman Who Laughs before his escape.
However, as the odds are increasingly stacked against the Justice League by the omnipotent villain Perpetua and the upgraded Legion of Doom, Batman reveals one final feature he secretly installed within the Hall of Justice in the event it was ever directly attacked. And this confidential upgrade is one that matches the Hall of Doom's own recently unveiled capabilities.
Lex Luthor revealed the Hall of Doom can transform into a flying warship, with metallic tentacles emerging from it like one of Brainiac's ships. As Lex leads the Legion on a final charge against the Hall of Justice and the assembled superheroes from across the DC Multiverse, Batman divulges that the headquarters can similarly transform into a battle station, and takes to the cockpit to face the Legion of Doom before the epic final confrontation for the fate of the DC Multiverse is joined.
It's unclear what the full capabilities of this mobile Hall of Justice are but, knowing Batman, he has likely packed the battle station with an arsenal of powerful weaponry and defensive systems to face the threats the League itself couldn't defeat. In a nod to the beginning of the previous issue, Batman hints the material helping to power the Hall of Justice's transformation is made from the same extraterrestrial material as the tomb for the recently fallen Starman, interred within the Hall in an alien stone that's highly durable yet lighter than air.
With both the Halls of Doom and Justice made mobile and the heroes and villains about to do battle in the streets of Washington, Snyder's epic run makes the promise of its climactic storyline "The Justice/Doom War" literal; the two factions are seemingly matched in every way. True to form, Batman has kept many secrets about the Justice League's latest headquarters from his teammates to pursue his own agenda. While Batman's shadowy prison facility for his Dark Multiverse doppelgänger ended up backfiring on him when the evil villain escaped literally right under the League's nose without their knowledge, his final secret about the building's offensive and mobile capabilities may be a key factor in turning the tide of battle against the Legion of Doom just when it seems like the League is hopelessly outgunned.