Phantom Zone

The Phantom Zone is a fictional dimension in the Superman comic books used predominantly before the DC Comics shared universe retcon with Crisis on Infinite Earths in the 1980s. It was discovered by Jor-El and used on the planet Krypton as a method of imprisonment of criminals. The Phantom Zone criminals first appeared in the Superboy stories and soon began appearing in the Superman stories.

The inmates of this dimension are cast into the dimension and reside in a featureless state of existence from which they observe, but cannot interact with, the regular dimension clearly. Inmates do not age or require sustenance in the Phantom Zone; furthermore, they are telepathic and mutually insubstantial.

As such, they survived the destruction of Krypton and focused their attention on Earth seeing as how most of the surviving Kryptonians now reside there. Most have a particular grudge against Superman seeing as how his father created the method of their own damnation. As such, they usually cause destructive trouble when they manage to escape while Superman struggles to return them to the Zone.

The only exception is Mon-El, a Daxamite youth who met Superman when he was Superboy on Earth and discovered he was acutely vulnerable to lead poisoning. To keep him alive, Superboy cast Mon-El, with his permission, into the Phantom Zone where he resided until the 30th century where Brainiac 5 of the Legion of Super-Heroes developed a cure which allowed him to leave safely.

Post Crisis

In the post-Crisis DC Universe, the Phantom Zone first appeared when Superman returned from space with a Kryptonian artifact called the Eradicator. This device, created by his ancestor Kem-L, attempted to recreate Krypton on Earth, building the Fortress of Solitude. The extradimensional space in which the Eradicator found the Kryptonian materials necessary was called the Phantom Zone.

A Phantom Zone Projector is part of Superman's current fortress. It has been used to access the Bottle City of Kandor and to trap villains such as the White Martians.

The Phantom Zone has also been independently discovered by the Bgzltians, the White Martains and the villains Loophole, Prometheus and Queen Bee, who call it the Buffer Zone, Still Zone, Stasis Zone, Ghost Zone and Honeycomb, respectively.