The Phantom Zone was an eerie twilight dimension used by the people of Krypton as a prison for the most dangerous criminals. Individuals banished to the Phantom Zone existed in a formless state, unable to affect or contact the normal world — for all intents and purposes, neither dead nor alive.
Jor-El, in the hours before Krypton's destruction, argued that the Phantom Zone might be used to save the Kryptonian people — that they could be suspended within the Zone until a single individual might travel by starship to a habitable world, and then release the survivors. The Science Council roundly rejected the proposal, objecting to the idea of imprisoning innocent people alongside criminals.
Nonetheless, a Phantom Zone projector was sent to Earth with Kal-El when Jor-El used his prototype starship to save his son from Krypton's doom. Years later, Superman would inadvertently release the criminals Jax-Ur and Mala from the Zone. The two would wreak havoc on Earth, even imprisoning Superman himself in the Zone: Superman was soon freed with the assistance of Professor Emil Hamilton, and the two criminals were ultimately returned to their extra dimensional prison.
Some time later, Superman and the other founders of the Justice League would imprison the destructive creature called Doomsday in the Phantom Zone, as no other method short of execution could reliably restrain the monstrosity.
Superman: The Animated Series
- "The Last Son of Krypton, Part I"
- "Blasts From the Past"
- "Absolute Power"
Justice League Unlimited
- "The Doomsday Sanction"