The offspring of Gaea the Earth and Uranus the heavens became known as the Titans of Myth. One such Titan was Mnemosyne, who along with partner / lover Crius was a Titan of Memory. Although the Titans of Myth enjoyed god-like status, Gaea had other less attractive offspring, whom Uranus banished to the pits of Tartarus.
Gaea persuaded Cronus to kill Uranus and release her brood. Instead, he killed Uranus and invited Mnemosyne and the rest of the Titans of Myth to join him in the paradise of a subjugated Earth.
Many years later, Cronus' own son Zeus overpowered his father and, having released the brood from Tartarus, he banished the Titans of Myth - including Mnemosyne - to imprisonment in stone pillars.
Thousands of years later, Thia and Hyperion managed to free themseles, and with the help of the Teen Titan known as Wonder Girl (Donna Troy) they went on to free Mnemosyne and the others. Mnemosyne then joined the rest of the Titans of Myth in two epic battles against the gods of Olympus.
During the second battle, Thia went insane and slew some of her own kind including Mnemosyne's partner Crius. As the fighting subsided, a contrite Zeus invited the surviving Titans of Myth to go and live with him in peace in the walls of Mount Olympus. Mnemosyne and the others agreed to do so.