Crisis on Infinite Earths #3

OBLIVION UPON US  Harbinger walks into the Monitor's sanctum as he continues testing young Alexander Luthor. Luthor is aging at an accelerated rate, and is now the physical age of an adolescent boy. The Monitor discovers he is composed of both positive matter and antimatter, and believes that this composite life form may hold the key towards stopping the Crisis. Harbinger, still under the influence of a dark, mysterious entity, leaves the Monitor's satellite and reports to her new master.