History: (JLA #77) - An unnamed extraterrestrial race created Mnemon to record their history, but the way it did so was to steal the memories of others. Essential knowledge of how to run the planet was lost, and the planet exploded when fusion reactors couldnolonge be maintained. Mnemon admired the destruction and considered it a work of art and itself an artist, a destroyer and a preserver rolle dinto one. It traveled from solar system to solar system systematically destroying civilizations. It landed on the moon near the JLA Watchtower and Atom and the JLA investigated. Atom entered Mnemon, who was quick to start eating the memories of the JLA. With Atom’s guidance Superman destroyed the magnetic field that kept it cohesive with his heat vision, but this freed the miniature black hole that powered Mnemon. It uploaded its memories into Superman to drive him mad, but through great force of will Superman held Mnemon and the black hole in his hands long enough tofly into space and toss it into a wormhole. It was now “insane” and the only data it retained was the melody of Stardust, the song Atom focused on to keep his memories from being absorbed by Mnemon.