Sailor Lethe is the one dressed in green, and Mnemosyne is the one dressed in pink. These two guarded the River outside of Galaxia's palace. That area was mainly desert so they are also called the 'Desert River Senshi'.
As Moon, Chibi Chibi, Starlights, and Princess Fireball arrive at the desert they don't know what to do next until they see a ferryman. The ferryman turns out to be Sailor Lethe. Lethe offered them a way across the desert, so the six got on the boat. Half way across the desert, the sand turned into water, and they all fell in. Moon woke up later as Bunny sitting on a swing in front of Lethe. She was holding the three moon cats, and she asked Bunny if they were hers. They still couldn't talk thanks to Tin Nyanko, but Bunny couldn't remember if they were anyway. Lethe destroys the cats, and seems to be trying to play mind tricks on Bunny to make her want to be alone. Mnemosyne comes in the scene right as Lethe is about to blast Bunny, and tells her that it is up to Galaxia to choose her fate (or atleast to put it into fewer words). As Mnemosyne says says Sailor Moon, Bunny remembers everything, turns back into Eternal Sailor Moon, and swims to her 'passed out' friends.
Lethe claims to be the leader of the River of Oblivion, and Mnemosyne the leader of the River of Memory.
Lethe is naturally mad that Sailor Moon got back her memory, and asked Mnemosyne if she betrayed her. Mnemosyne answers that she just didn't want a fellow Senshi to be hurt by Lethe. Mnemosyne then puts the senshi on dry land, and gives Fireball some 'memory water' when she wakes up because is was as confused as Moon was.
Lethe is not very happy with this, and informs the two awake senshi that they will not leave the desert alive.
A conversation between Lethe and Mnemosyne reveals that they were from different planets (the planets that they are named after) and that the planets were filled of choas until Galaxia brought silence (death). They both just want peace, and they think that Galaxia will bring that peace, and Mnemosyne thinks there is no reason to keep up war if they want peace.
Fireball tells the two that Galaxia will always bring Destruction and War, so Lethe asks is Sailor Moon could then bring peace. Lethe thinks that if Sailor Moon doesn't die then the war will still go on. Moon tells them that she also came here to end the war, and that if ending it means to kill her then that they should.
Mnemosyne and Lethe start to let them go, and the Starlights wake up still confused.
Two animamates appear and blast Lethe and Mnemosyne for not killing the senshi. The animamates also took the Starlights seeds.
~Back to The Lethe and Mnemosyne Shrine~