WARNING: The following article contains spoilers for "The Fall of Earth" in Dark Nights: Death Metal Guidebook #1, by Scott Snyder, James Tynion IV, Joshua Williamson, Doug Mahnke, Jaime Mendoza, David Baron and Tom Napolitano, available now.
At the end of Dark Nights: Death Metal #3, we learned that the alien bounty hunter Lobo was working for Lex Luthor. Luthor hired Lobo to collect pieces of a material he calls Death Metal from across the universe. The purpose of this special metal isn't revealed yet, but it appears Luthor intends to use it to help defeat the Batman Who Laughs. It may even bring the world back to what it was before it was destroyed and remade into a dystopian nightmare.
But that's not all that Luthor is doing. In Dark Nights: Death Metal Guidebook #1, we see the Superman villain pay a brief visit to Earth before returning to his hiding place on the Moon. And it's there he reveals the next part of his plan: he's bringing the Legion of Doom back together.
Lex Luthor first assembled his version of the Legion of Doom at the start of Scott Snyder and Jim Cheung's Justice League #1. Luthor formed the supervillain team which included Sinestro, Cheetah, Black Manta, Gorilla Grodd and the Joker. The purpose of this new team was to battle the Justice League, of course, while Lex Luthor played a long game to collect the cosmic weapon known as the Totality.
This was all part of an overarching plot that would see Lex and his Legion free the Mother of the Multiverse, Perpetua. Then, after the all-powerful cosmic being transformed him into an Apex Predator, Luthor led the Legion in an extended battle against the Justice League for the fate of the entire universe called the "Justice/Doom War." Over time, the Legion would lose Joker and Black Manta, but it would gain a powerful new ally in Brainiac.
For two years, the Justice League and the Legion of Doom were locked in a race, two opposing forces dueling for the fate of reality. This all, of course, culminated with the destruction of the DC Universe as we know it and the formation of a new world dominated by the Batman Who Laughs in Death Metal #1.
Luthor may have been successful in unleashing Perpetua, but he was eventually defeated, betrayed, and discarded. The Mother of the Multiverse favored the Batman Who Laughs over him and now, the Superman villain appears to be trying to undo everything that he initially caused.
In Death Metal Guidebook #1, Luthor returns to his mobile Hall of Doom, which is currently located on the Moon, where he finds Lobo. There, he instructs the alien to once again hunt for the Death Metal, while he will gather his own forces. These forces, as we see, are the members of his old team: Gorilla Grodd, Cheetah, Sinestro, and Brainiac.
The last we saw of the Legion of Doom was at the end of the Justice/Doom War. However, their whereabouts remain unknown in the new reality of Death Metal. It's likely they too are somewhere on Earth and when Luthor finds them, he will assemble a team that may make the difference in the coming confrontation.
This all started with the Justice League and the Legion of Doom at war, but bringing those two teams together might be the only way to save the DC Universe.