The discovery of the Dark Multiverse is one of the biggest shifts to the cosmology of the DC Universe since it the Multiverse itself was brought back ten years ago in 52. While the positive multiverse has a structure and an order, the Dark Multiverse is a swirling sea of humanity’s worst nightmares made up out of worlds too chaotic to be considered viable, worlds doomed to destroy themselves like the tide crashing against the shore.
We’ve been given a couple of glimpses at the Dark Multiverse in the pages of Dark Nights: Metal, but its in the event's one-shots starring The Dark Knights themselves — alternate, evil versions of Batman mashed up with other Justice Leaguers — where we’ve really had the chance to take a good look at the specific worlds of the Dark Multiverse, which may hold the key to understanding them.
To understand the Dark Multiverse, first we have to understand The Multiverse, which can be a lot to take in. A quick timeline works like this: There were infinite universes, then there was one combined universe, then there was a multiverse again, but this time featuring just fifty-two worlds. The Multiverse of 52 worlds was created during Infinite Crisis, though the heroes of the DC Universe didn’t discover this fact until roughly a year later when Booster Gold and Rip Hunter stumbled upon the secret in their battle against Mister Mind. The Multiverse we have today is slightly different from that one following the changes made in Flashpoint, but they’re pretty similar overall.
Writer Grant Morrison forged the Multiverse into a somewhat easy-to-understand cosmology ahead of the release of The Multiversity, a series Morrison wrote which hopped from different worlds as part of a giant adventure which involved direct communication between the comic book and the reader themselves as the villain. Morrison not only established the fifty-two worlds, he established a logic to their placement on an actual map. For example, Earth 20 — the home of the pulp-inspired Society of Super-Heroes — is directly opposite Earth 40, the home of their counterparts, The Society of Supervillains. The Nazi planet Earth 10 is opposite Earth 5, placing DC’s acquisitions from Quality Comics and Fawcett Comics on opposite sides of the map.