In the 2017 DC Comics major event "Dark Nights," the main editor of "Batman," Scott Snyder, brought us a grand legend about a "Batman Alliance," but these seven Batmen from different universes did not come to save the world; they came to destroy it.
The origin of the matter was that Batman of Earth 0 was secretly fed five special metals from the cosmos, making him a gateway for summoning the Dark Dragon Barbatos. Although Master tried various ways to prevent the summoning conditions from being fulfilled, he ultimately failed. Batman of the Main World was replaced, and with that came seven warriors brought by Barbatos from the Dark Faraway Universe—the Dark Knight Order.
The Dark Multiverse is one of the worldviews in DC Comics, introduced in "Metal," created by Scott Snyder and Greg Capullo. It exists on the reverse side of the Multiverse of the DC Universe. The Dark Multiverse is filled with stories that should never play out; they are twisted, deformed, and struggle desperately to survive under the true Multiverse's brilliance.
Below is Tuanzi's personal understanding. In the book, Tuanzi calls the Dark Multiverse simply "Negative," a shorthand representing how their world is more negative. Personally, I habitually refer to Earth 0 as the Main World, though this naming isn't very precise.
This major event is more like a super individual issue about Multiverse Batmen, where the events happening to the Batman in the Dark Multiverse are various possibilities of Batman going bad.
The event describes many instances of the seven mad Batmen, and the biggest reason they ended up like this is regret, attempting to correct their mistakes, only to make things worse, ultimately destroying the world.
Barbatos reaches the Main World, binding all of humanity to the Dark Tower and transforming them into batteries, trying to convert everyone's negative emotions into Dark Energy to pull the Bright Multiverse into darkness.
The comic tells the story of the Justice League and other heroes battling against Barbatos.
Tuanzi selected this major event as the beginning of the entire book, primarily because it introduced the concept of the Dark Multiverse, greatly expanding the world.
Secondly, during the battle, the Origin Wall of the DC Universe fractured, and beyond the wall lies the unknown, creating endless possibilities.
Lastly, in the comic, Earth -11, such a beloved gender-swapped world, was casually destroyed. Tuanzi wants to change this ending, merely using DC's gender-swapped characters; the story is entirely original, and there is no comic plot to reference.
Well, that's it meow, the Metal major event is just the beginning of the entire book, and the protagonist still has a long way to go.