WARNING: The following contains spoilers for Infinite Frontier #4, on sale now from DC.
With the DC Multiverse reborn from the cataclysmic fires of Dark Nights: Death Metal, the general public is now well aware of the existence of alternate universes and divergent timelines while the superheroes from across the multiverse band together to form their own team, Justice Incarnate. This multiversal Justice League is dedicated to defending all of the rapidly expanding Omniverse from further threats to all of reality while investigating the new mysteries of the post-Death Metal landscape. And as Justice Incarnate decides to travel to Earth Omega to rescue their teammate Barry Allen from the clutches of Darkseid, they are betrayed by one of their own: Machinehead.
Created by Grant Morrison and Ivan Reis in 2014's The Multiversity #4, Machinehead is from the alternate universe of Earth-8. This particular world is a thinly veiled analog for the Marvel Universe, with the universe defended by a superhero team known as the Retaliators rather than the Avengers. The Retaliators' various members are pastiches of iconic Marvel superheroes, with Machinehead serving as the team's analog to Iron Man, albeit horrifically scarred and deranged from his experiences. Machinehead was chosen to represent Earth-8 on Justice Incarnate, with his technological expertise proving invaluable for the multiversal team. However, in Infinite Frontier #4 -- by Joshua Williamson, Paul Pelletier, Jesus Merino, Xermanico, Norm Rapmund, Raul Fernandez, Hi-Fi and Tom Napolitano -- Machinehead reveals his true, sinister agenda before his backstabbed teammates.
As the team conducts a murder mystery to learn who killed Earth-23's Lex Luthor, suspicions begin to mount between the team that one of them might be responsible for the detected anomalies. Flashpoint Batman faces a fair amount of suspicion due to his entire timeline being erased, but this falls on the backburner when President Superman realizes the Flash is stranded on the ominous Earth Omega. Before the team can mount a rescue, however, Machinehead strikes, incapacitating several of his teammates with energy blasts before calling in a team of his own to confront Justice Incarnate.
Machinehead reveals that he has no intention of destroying the multiverse but wants to prevent further crossovers to mitigate the chances of reality being threatened as universes come together. This lines up with Mister Bones' goals for the D.E.O., with the master spy going as far as to patrol the Bleed between universes and team up with supervillains to ensure no further incursions into the main DC Universe take place. And Machinehead's own network of alliances has him form Injustice Incarnate, assembling various formidable villains and antiheroes together to attack the House of Heroes and dismantle Justice Incarnate's efforts.
With reality and the multiverse still in such a fragile state following Death Metal, both Mister Bones and Machinehead are determined to keep the universes separate to avoid any further catastrophes. This has led both characters to launch their own epic betrayals, and while Bones betrays the DCU's superhero community, Machinehead appropriately takes his backstabbing to a multiversal level. And in control of the House of Heroes' tech systems and catching the team off-guard, Machinehead and his newly unveiled Injustice Incarnate places the heroes on the defensive on their own home turf as the fight to protect the multiverse takes a shocking turn -- with friends quickly becoming foes.