From the oracle Manga: It is then revealed that Lethe and Mnemosyne are the senshi of the planets Lethe and Mnemosyne, respectively. Their planets were small, poor, and plagued by violence and chaos. Galaxia appeared and brought death and ruing to the planets, and the two had no choice but to follow her in the hopes of someday finding peace. Lethe says that Sailor Moon's Sailor Crystal, the Ginzuishou, is the cause for all of the wars they are experiencing, and that if it is destroyed, there will be peace. Sailor Moon offers her life if it will end the violence. Lethe and Mnemosyne are so moved by her self-sacrifice that they realize that whether or not Sailor Moon dies, the war will continue. Just as they are about to release the senshi, Sailor Chi and Sailor Phi appear, calling them useless fools and taking their Sailor Crystals, killing them. Lethe and Mnemosyne can be distinguished because Lethe wears a darker green dress, while Mnemosyne wears a lighter pink dress. Lethe appears harsher and more cruel than Mnemosyne, who appears softer and more feminine. Their facial features compliment their personalities. The two are often called the Desert River senshi, because the guard the desert rivers of Oblivion and Memory. The Materials Collection states that the two are twins.