Starfinger is a mysterious and powerful criminal from the 30th century who possesses the ability to fire a variety of beams from his right hand. Each ray has a specific negative action on a member of the Legion of Super-Heroes (for example, making Light Lass "super heavy", transforming Phantom Girl into a permanent phantom, and a focused kryptonite projection to handle Superboy). The true identity of the helmeted Starfinger is eventually sensed by Saturn Girl as being that of one of the Legionaires themselves (Adv No. 335, Aug 1965: "Starfinger!").
It is finally revealed that Starfinger is actually a mind-altered Lightning Lad who has been controlled to act on behalf of the "real" Starfinger - the evil Dr. Hanscom (Adv No. 336, Sep 1965: "The True Identity of Starfinger!").