Ace Arn was from an unspecific time in the future were space travel was common. One day, he crashed on an alien planet. Four aliens from four other planets shot him with ray guns that were supposed to turn him into one of them. But, they all fired at the same time. As a result, each quarter of his body was transformed to be like that of one of the aliens, giving him a very Metamorpho appearance (and a combo of their super powers). Combining the first letters of the home planets the alien and the first one of his name, he got U-L-T-R-A, and dubbed himself "Ultra". He discovered a device that could turn him back to Arn and vise versa. He had several adventures in Mystery in Space, till the comic got axed.
Wizard Magazine featured Ultra as the "Mort of the Month", a featurette showcasing low-quality characters. Grant Morrison used the character in Animal Man (as a denizen of Limbo) and in the Aztek mini-series. In Starman # 55, he, with the aid of Space Ranger, looked for the fourth Starman's cosmic staff. In the Stars and S.T.R.I.P.E. storyline, Young Justice, Star-Spangled Kid and S.T.R.I.P.E. tried to stop a group of Larroo (one of the aliens that attacked Ace and turned him into Ultra), who plotted to turn everyone in Blue Valley into Larroo. It was also mention while the Larroo invented the ray they sold it to other races. In Infinite Crisis, Ultra (somehow) traveled back in time to the present and (with other space-themed heroes) aided Donna Troy in the fallout caused by the Rann-Thanagar War. In Superman/Batman # 31, he was among the alien heroes being overwhelmed by an alien force and went on a rampage. In issue 33, he (with the mind-controled alien heroes) tried to destroy the titular characters, but his mind was released from the mind control and Despero (who did the mind control) was defeated. In Action Comics # 867, Brainiac attacked the planet Larroo. Superman could do nothing as Brainiac capture (and shrunk) a city, containing the four races that were involved with Ultra's origins, that was trapped in a force field created by Ultra. The aliens' sun was destoryed. In the same storyline, Ultra appeared as one of the heroes fighting Brainiac on his ship. Although he hasn't appeared recently, Vixen (half-jokingly) says he is a potential Justice League member.
Each quarter of his body (and it's limb) has a different power. They were:
- The upper right of his body was super strong.
- The upper left has magnetic powers.
- His right leg gave him flight.
- His left leg is a bolt of lightning.