The Green Lantern and Sinestro Corps now under Soranik Natu form an alliance against the encroaching Dark Multiverse. Sinestro initially plans to cooperate but is met at the Source Wall by Lex Luthor, who invites Sinestro to Earth to join his Legion of Doom. Attracted by the promise of the "Invisible Emotional Spectrum", a source of power Sinestro became aware of in his youth just before joining the Green Lanterns, Sinestro abandons the Corps and travels to Earth. Reverting to his original Silver Age costume, and wielding the power of the Ultraviolet Corps rather than his Qwardian power ring, he successfully brainwashes half the planet and begins to bring the black sun Umbrax, source of the Invisible Spectrum, into the universe. After the plan is foiled, he remains an ally of Luthor.