Radiant was a member of Clock King's gang the Clockwatchers. This was a group put together to attack the Teen Titans while they promote their latest line of action figures at a toy store. Radiant expressed worry that they'd actually seriously injure the Titans…he was fighting with radiation after all. After being assured that the Titans were tough, Radiant takes on the Atom, who was leading the team at the time. The Atom hides from Radiant among a bunch of spilled action figures, leaping up and knocking out Radiant after a little while. Radiant was arrested and taken away to await trial.
Radiant has the power to shoot radiation beams from his eyes.