Born on Rimbor, a world full of criminals and low-lifes, Jo learned tactics of survival through combat and strategy from an early age. One day, while attempting to avoid a group of men out to kill him, he accidentally piloted his ship too close to a gigantic Space Whale. He was consumed by the whale, and forced to survive for weeks on end in the creature's stomach. With nothing else to eat, he was forced to eat parts of the whale itself, which imbued him with special abilities. After fashioning makeshift oxygen containers involving usage of the beast's stomach acid, Jo was able to fly out of the whale and escape back to Rimbor.
Ultra Boy joined Leland McCauley's Workforce, but became more closely affiliated with the Legion when he met Tinya Wazzo, Apparition, whom he began a romantic relationship with. Eventually, because of McCauley's corrupt business practices, he would quit the Workforce. Although he aided the Legion for a short time, he was unable to actually join the government-sponsored team because of the policies of U.P. President Jeanne Chu, although she was eventually deposed from office through criminal charges. When her replacement, R.J. Brande expanded the Legion's membership policies, Ultra Boy became a full-fledged Legionnaire.
Ultra-Energy Empowerment: Ultra Boy can utilize the ultra-energy in his body in a variety of ways, but only one at a time. He can utilize it for any of the following:
- Ultra-Strength: When Ultra Boy uses this power he is many times stronger than usual. His strength enables him to lift far in excess of 100 tons. He has strength rivaling that of powerhouses like Superman, Captain Marvel and Martian Manhunter.
- Superhuman Stamina: Ultra Boy could sustain prolonged physical exertion without tiring or undo strain for an indeterminate period of time.
- Ultra-Speed: Ultra Boy could run at a velocity many times greater than that of a normal human being. Unlike other super-speedsters however, Jo Nah's "Ultra-Speed" is not rooted in the Speed Field, and thus he has no physical connection to the Speed Force.
- Super-Breath: Ultra Boy possessed the ability to create hurricane force winds by blowing, and to chill an his breath in order to freeze a target. This ability has also been referred to as "Ultra-Breath". Ultra Boy could also breathe in large amounts of air, an ability used when dealing with and disposing things like clouds of poison gas.
- Ultra-Invulnerability: When using this power, he is impervious to harm by nuclear forces. If propelled at sufficient force, by either his flight ring or a super-toss, Ultra Boy can use his ultra-hard body like a human missile.
- Flight: Ultra Boy could fly by psionically manipulating a planet's gravitonic field. Although he did not require the use of a Legion Flight Ring, he still wore one in recognition of his commitment as a Legionnaire.
- Ultra-Vision: Ultra Boy's penetra-vision makes him able to see through solid matter, although he appears to be unable to see through lead. As part of his same ultra-vision power, Ultra Boy can use telescopic vision, in combination with penetra-vision if desired. He also has microscopic-vision and is able to analyze fingerprints.
- Energy Projection: Another vision-based power, Ultra Boy could project beams of concentrated thermal energy from his eyes, which he referred to as "Flash Vision". Flash vision works along the same properties as Superman's Heat Vision.
- One Power at A Time: As mentioned above, one serious limitation to his ultra-powers is that he can only use one at a time. This means that if he wants to fly through space at super-speed he must wear a spacesuit to survive in the cold vacuum. When using his power for super-strength he is not invulnerable and can therefore get tired, feel muscular pain or even pull a muscle.
- Legion Flight Ring: All Legionnaires were presented with a flight ring that enabled them to defy gravity and sustain movement through the air by aerodynamically generating force.
Post Zero-Hour Jo Nah's mother never married Jo's father and claims to not even know who he is.
- 146 Appearances of Jo Nah (Post-Zero Hour)
- 11 Images featuring Jo Nah (Post-Zero Hour)
- 6 Quotations by or about Jo Nah (Post-Zero Hour)
- Character Gallery: Jo Nah (Post-Zero Hour)
Legion of Super-Heroes member