The pocket universe: Lex Luthor's prison in Superman 2025 and its origin with the Time Trapper

Lex Luthor's pocket universe, a prison outside our reality

In James Gunn's Superman, the pocket universe is an artificial dimension that Lex Luthor built from scratch. The billionaire played by Nicholas Hoult hides a secret prison there, beyond the reach of the law and out of sight. On screen, Lex explains that he created this dimension by replicating the Big Bang with a megacollider belonging to LuthorCorp, his company. Dimensional portals connect this closed world to ours, and Lex and his men alike pass through them to get in and out.

James Gunn insists on a distinction. Interviewed by Rolling Stone in July 2025, he says he doesn't like teleportation and sees the pocket universe as travel from one point in dimensional space to another. In the same answer, about the Legion of Super-Heroes, he says he isn't drawn to time travel. In April 2025, he was already listing pocket universes among the fantastical elements “never really seen in a Superman movie,” alongside the flying dog and the giant kaiju.

Cube-shaped cages: who Lex locks up in his dimension

The film shows a prison made of cube-shaped cages stacked as far as the eye can see. Production designer Beth Mickle had nine of these cubes built, three wide by three high, which the visual effects then multiplied in every direction. Wētā FX turned them into a mathematically inspired world of countless cubes and crystalline metal structures plunged into darkness.

In the film, the prisoners are a very mixed group: political opponents from several countries, people who simply crossed Lex, former girlfriends and metahumans like Metamorpho, whose infant son, Joey, is also being held by Lex. Krypto, the dog Superman is looking after for his cousin Kara, is held there after his capture at the Fortress of Solitude. Superman also comes across a horde of monkeys flooding social media with hostile posts about him.

To get around his prison, Lex relies on Mister Handsome, the creature that pilots the pocket universe's platform. According to James Gunn, Lex created it at age 12 in a Petri dish while trying to make a human being, and it may be the only creature he truly cares about. Trevor Newlin plays it on screen.

Superman surrenders, Lex interrogates him and shoots Malik Ali

In the film, Superman doesn't end up in this prison as the result of a fight. Lex has released the second half of the message from Jor-El and Lara, in which Kal-El's Kryptonian parents urge him to conquer Earth, and public opinion has turned against the hero. Superman surrenders to the US government, which hands him over to Lex to detain and interrogate. He shares a cell with Metamorpho, who must turn one of his hands into kryptonite or see Lex harm Joey: stripped of his powers, Superman is left at the mercy of his jailer.

The interrogation turns into blackmail. Lex has Malik Ali brought in, a falafel vendor and Superman supporter played by Dinesh Thyagarajan, and shoots him in the head in front of Superman, in the presence of Vasil Ghurkos, the president of Boravia. James Gunn has said he cut an even darker continuation of the scene very early in editing, in which Lex made Ghurkos lie down in the blood to protect his shoes. This murder convinces Metamorpho to switch sides.

The escape: a miniature sun, the River Pi and a black hole

In the film, a horrified Metamorpho creates a small sun whose light restores the Kryptonian's strength, as the light of a yellow sun usually does. Superman breaks out of his cell and frees Joey, then Krypto. Meanwhile, Lois Lane, played by Rachel Brosnahan, asks the Justice Gang for help, and only Mister Terrific agrees. At Fort Kramer, he takes out Lex's Raptors in one long continuous take, then enters the pocket universe with Lois.

The escape gets more complicated. Weakened by kryptonite and under attack from the Raptors, Superman, with Joey in his arms, is swept away by the River Pi, a river of antiprotons that empties into a black hole. Metamorpho, Krypto and one last burst of super-breath pull him out, then Mister Terrific's flying spheres guide the group to the portal, which they get through just before it collapses. On set, according to Guy Williams, visual effects supervisor at Wētā FX, the river was a pool filled with hundreds of thousands of roll-on deodorant balls.

The rift that splits Metropolis in two

After the escape, Lex puts his dimension to use again. In the film, Eve Teschmacher, his girlfriend played by Sara Sampaio, passes the evidence of the deal struck between Lex and Boravia to Jimmy Olsen, played by Skyler Gisondo. When Lex discovers she's in contact with Jimmy, he has Eve locked up in the pocket universe. To lure Superman, he opens an unstable portal to his prison: the rift that opens up splits Metropolis in two.

Superman and Mister Terrific then face the Engineer and Ultraman. Superman defeats the Engineer, learns that Ultraman is his clone, created by Lex, then, with Krypto's help, hurls him into a black hole that has opened beneath the rift. The film doesn't say whether Ultraman survives. Mister Terrific closes the rift from Lex's headquarters, Lex ends up under arrest, and the prisoners of the pocket universe, Eve among them, regain their freedom.

James Gunn himself compares this dimension to the Quantum Unfolding Chamber, the pocket universe at the heart of season 2 of the series Peacemaker, and considers Lex's far more rickety.

1987: the Time Trapper's pocket universe, built around Superboy

In the comics, the idea grew out of a continuity puzzle. After Crisis on Infinite Earths, John Byrne's The Man of Steel miniseries told a new origin in 1986, in which Clark Kent had never been Superboy. But Superboy had inspired the Legion of Super-Heroes, the 30th-century team he had joined. DC fixed this inconsistency with a four-issue crossover, cover-dated August and September 1987: Legion of Super-Heroes (vol. 3) #37 and #38, by Paul Levitz and Greg LaRocque, bookended Superman (vol. 2) #8 and Action Comics #591, both by John Byrne.

In Action Comics #591, cover-dated August 1987, the Time Trapper, a Legion foe introduced in the 1960s, reveals his trick. He has carved a pocket universe out of a slice of space-time, with its own Earth, its own Krypton and its own Superboy, and has been diverting the Legion there every time it thought it was traveling back in time to Superboy. The 1988 issues would specify that only Earth and Krypton harbored life there. This Superboy has nothing to do with Kon-El, the clone who would take up the name in 1993.

In Legion of Super-Heroes (vol. 3) #38, cover-dated September 1987, this Superboy sacrifices himself to save his Earth, then dies of his wounds once he reaches the 30th century with the Legionnaires.

A heroic Lex Luthor, three Kryptonians and a dead Earth

John Byrne returned to the pocket universe in 1988, with a Lex Luthor far removed from Superman's sworn enemy. In these comics, the pocket universe's Lex is a heroic scientist. While searching Superboy's old laboratory for any trace of him, he is tricked by three criminals from his world's Phantom Zone, General Zod, Quex-Ul and Zaora, and sets them free. The three Kryptonians ravage the planet. Lex organizes the resistance and creates a synthetic Supergirl, who first appeared in Superman (vol. 2) #16, cover-dated April 1988.

In Superman (vol. 2) #21, cover-dated September 1988, the survivors of that world bring in the Superman of the main universe. He finds a devastated Earth, where the three criminals have killed almost the entire population. At the end of the story, Supergirl, badly wounded, is the only survivor of that Earth, and Superman takes her back to his own world, where she moves in with the Kents.

Superman #22: the execution that haunts the Man of Steel

The climax comes in Superman (vol. 2) #22, cover-dated October 1988, written and drawn by John Byrne. Immune to that universe's kryptonite, Superman finds gold kryptonite in Superboy's old laboratory and uses it to strip Zod, Quex-Ul and Zaora of their powers. Yet the three criminals swear that one day they will regain their strength and reach his Earth to attack him and his world.

The Phantom Zone projector has been destroyed, and Superman can neither imprison them on his Earth nor leave them on this dead world, from which they could return. He executes them with that universe's green kryptonite, then buries their bodies. The act haunts him in the following issues: consumed by guilt, he eventually goes into exile in space, where Mongul's ship captures him. This execution remains an exception to Superman's moral code, which normally forbids him to kill.

From the Time Trapper to Lex Luthor: two pocket universes, two executions

The 2025 film never mentions the Time Trapper, and the Legion of Super-Heroes doesn't appear in it. Its pocket universe doesn't come from tampering with time: Lex builds it with a machine, and James Gunn thinks of it as movement through dimensional space. The term also exists in cosmology, where physicist Alan Guth calls the regions produced by eternal inflation pocket universes.

Yet the two versions echo each other. In the 1987-1988 comics, the pocket universe's kryptonite does nothing to Byrne's Superman; in the film, kryptonite produced on site drains his strength. The Lex of the 1988 comics is a heroic scientist; the film's Lex is a jailer. Above all, each pocket universe is the setting for an execution: in 1988, Superman kills three criminals there who had wiped out a planet's population, while in 2025, Lex shoots a civilian there to break the hero.

Conclusion

In the 2025 Superman, the pocket universe is Lex Luthor's private prison, a world of cubes where Superman loses his powers, watches Malik Ali die and narrowly escapes the River Pi. In the comics, the idea has a precedent: the pocket universe the Time Trapper builds in the 1987 crossover by John Byrne and Paul Levitz.

From one version to the other, the roles are reversed. In 1988, it's Superman who kills in the pocket universe, breaking with his usual refusal to kill; in 2025, it's Lex Luthor who shoots an innocent man there.