Sailor Mnemosyne

セーラー・ムネモシュネ

Sailor Lethe and Sailor Mnemosyne appear exclusively in Act 48 of the manga. They are twin sisters originating from the planets Lethe and Mnemosyne, respectively. Their home worlds were small, impoverished, and ravaged by violence and chaos. When Galaxia arrived, bringing death and ruin, the sisters had no choice but to follow her, hoping to eventually find peace.
Sailor Mnemosyne takes her name from the Titaness of memory, mother of the muses, as well as from another river in the underworld associated with remembrance and omniscience.
Sailor Lethe initially introduces herself as the ferryman of the desert river. She traps Eternal Sailor Moon at the bottom of the River of Oblivion, kills Luna, Artemis, and Diana, and attacks Sailor Moon. She is halted by Sailor Mnemosyne, who states that Sailor Moon has suffered enough.
Lethe claims that Sailor Moon's Sailor Crystal, the Ginzuishou, is the cause of all the wars they are enduring, and that destroying it will bring peace. Sailor Moon offers her own life if it will end the violence. Lethe and Mnemosyne are so moved by this self-sacrifice that they realize the war will continue regardless of whether Sailor Moon lives or dies. Just as they are about to release the Senshi, Sailor Chi and Sailor Phi appear. These two call Lethe and Mnemosyne useless fools and take their Sailor Crystals, killing them.