Radster was a monstrous alien that worked for Scorpius and confronted the Galaxy Rangers after they made Brunt retreat in their attempt to rescue the Galactabeasts. But he himself retreated when the Rangers released the space creatures. Radster later attacked Terra Venture with Furio and was destroyed by the Lion Galactabeast. He sounds and talks like Elvis Presley.
In "The Sunflower Search," Radster was featured in a flashback as part of Scorpius' attack upon the Magna Defender's planet 3,000 years ago.