Created by writer Otto Binder and artist George Papp, the character first appeared in Adventure Comics #289 (October 1961).

[4] He was sentenced to life imprisonment in the Phantom Zone for destroying Wegthor, a sparsely inhabited moon of Krypton, while experimenting with a nuclear warhead.

Jax-Ur later helps Superman defeat Black Zero, the alien saboteur who ensured Krypton's destruction, before willingly returning to the Phantom Zone.

[1] He builds a device tailored to regulate Chris's growth and stimulate his solar-powered healing factor to reverse the body damage done by his condition.

[16] Jax-Ur was fully introduced in the World of Krypton flashback segments, where he is depicted as a young military officer and Lara's partner and fiancé.

[17] Lara calls off their engagement when Jax-Ur reveals he supports Colonel Ekar, a commanding officer who deems Krypton's Science Council weak and self-absorbed and plans to overthrow it with a coup d'état.

When Lara tries to fight Colonel Ekar and is defeated and caught, Jax-Ur tries to convince her to join their cause in order to save her life, but fails.

In addition to his inherent Kryptonian abilities while beneath a yellow sun, Jax-Ur also served as a vessel for the alien god Vohc the Breaker.

Similar to General Zod and other Phantom Zone escapees, Jax-Ur generally never experiences the full measure of his abilities as he is never allowed to spend any significant portion of time beneath Earth's yellow sun to charge and metabolize his cells with yellow solar radiation before being banished back into the Zone.

This version became a martyr after inspiring a group of protestors who consider his imprisonment in the Phantom Zone to be cruel and unusual punishment and seek to free him.