The Phantom Zone has also served as a sanctuary of sorts for characters such as the Daxamite hero Mon-El, who was relegated to its timeless landscape in the hopes of staving off a lethal dose of lead poisoning.

WARNING The following contains major spoilers for Action Comics #1071, on sale now from DC Comics.

Over the years, the Phantom Zone has been a home and prison to a myriad of iconic DC Comics characters, including Hank Henshaw, the Cyborg Superman, and even General Zod, quite possibly the Phantom Zone's most infamous prisoner. This concept has been revisited in numerous DC storylines, ranging from multiple comic book events to live-action adaptations including multiple Arrowverse appearances on various CW series. The Phantom Zone has also served as a sanctuary of sorts for characters such as the Daxamite hero Mon-El, who was relegated to its timeless landscape in the hopes of staving off a lethal dose of lead poisoning.

The modern day Phantom King, Xa-Du, was the first Kryptonian ever sentenced to imprisonment within the Phantom Zone. Formerly a scientist on Krypton, Xa-Du experimented in the realm of suspended animation, although his inhumane methods led to his research being suspended and his ultimate incarceration. Eventually, Xa-Du was able to develop the technology that allowed him to escape the Phantom Zone altogether, only to be defeated by the likes of Supergirl and sent back for his troubles.

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https://www.cbr.com/superman-new-phantom-zone-ruler-revealed/