Mistress 9 is the Messiah of Silence. She is an evil spirit who serves Pharaoh 90.
In the anime
After being possessed by Germatoid, Professor Tomoe and the Heart Snatchers chose Tomoe's daughter, Hotaru, to be the host of Mistress 9. She needed Pure Hearts to increase her power, which is why Mimet continued seeking out Pure Hearts. Eventually, with the help of Kaorinite, Mistress 9 was able to take Rini's Pure Heart and awaken in her true form. Saying that Kaorinite served her purpose and is not needed anymore, Mistress 9 killed her with a bolt of electricity. Sailor Uranus and Sailor Neptune attacked Mistress 9, but Sailor Moon jumped in front of her and took the attack to protect Hotaru. Mistress 9 threatened to kill Sailor Uranus and Sailor Neptune unless Sailor Moon gave her the Holy Grail.
Professor Tomoe, now free of Germatoid's control, appeared, and Hotaru appeared to regain control and ask for the Holy Grail to return to normal. This was a trap, however, and it worked; Sailor Moon and Professor Tomoe gave her the Purity Chalice, and she used it to summon Pharaoh 90, destroying the Purity Chalice in the process. However, she was attacked by Pharaoh 90, but was protected by Sailor Moon and Professor Tomoe. Hotaru ultimately overpowered Mistress 9 with memories of Chibi-Usa and Tomoe, and she was destroyed.
- Mistress 9 is the Wicked Lady and Evil Prince Darien of Sailor Moon S. She is possessing Hotaru, and before the final battle, Hotaru eventually destroys her and returns to normal, similar to before the final battle, Beryl's spell over Darien is broken, and Wicked Lady is turned back into Rini. The difference is, while the previous two were merely turned evil, Mistress 9 is an entirely different entity possessing Hotaru.
- Mistress 9 looks similar to Sailor Mars and Sailor Pluto.
- She is the second character to kill Kaorinite.
Voiced by Jennifer Gould in the English anime