Nemesis (ネメシス), also known as the Dark Moon (暗黒の月), was the tenth planet of the Solar System, and the location of the Black Moon Castle, the seat of the Black Moon Clan's power. The planet itself was made of Evil Black Crystal, which was capable of absorbing light, much like a black hole. This would cause the planet to appear and disappear from the sensors tracking it in Crystal Tokyo, making its orbit seem erratic and difficult to trace. For a long time, the planet remained cloaked in darkness, but some time in the 30th century it began to emit large amounts of negative energy, indicating its presence.
Soon after the creation of Crystal Tokyo, there was a challenge to the peace made by the Death Phantom. Because he was human, Neo-Queen Serenity did not want to kill him, so she banished him to the planet Nemesis and it became forbidden. Many years later, there was another revolt on the Earth. After the battle, those who did not want to stay left Earth and ended up on Nemesis where they came under the influence of the Death Phantom.
At some point in time, the Death Phantom lost his physical body and his will became one with the planet.
In the manga and Sailor Moon Crystal, Sailor Mars, Sailor Mercury, and Sailor Jupiter were captured and held in the dungeon on Nemesis.
- The planet Nemesis may have been named for a theoretical star credited for mass extinctions on Earth.
- Nemesis was also the goddess of revenge and divine retribution in Greek mythology, and the word is now used to describe one's greatest rival or enemy.
- The center of Wiseman's power, hidden within Nemesis, was called ワイズマンの暗黒城 (Waizuman no Ankoku Joo; Wiseman's Dark Castle), or in the Materials Collection, simply ワイズマンの城 (Waizuman no Joo; Wiseman's Castle).
- Fans who create Otaku Senshi often like to invent a "Sailor Nemesis," as there was no mention of one given in the series.
- In the German dub of the anime, the planet was called "Menesis."