The evil being which takes over Hotaru's body is Mistress 9. She's a very beautiful woman with long, flowing hair. This hair actually comes to life and attempts to strangle and kill the senshi.

In the anime, Hotaru becomes Mistress 9 when she takes the energy from Chibi-Usa's heart crystal. In the manga, she becomes Mistress 9 because of an egg implanted in her by her father. Either way, Mistress 9 is a very deadly and strong opponent.

In the manga, Mistress 9 steals Chibi-Usa's ginzuishou, thus stealing her spirit as well. Sailor Neptune and Uranus are mad about this, but mainly that they did not arrive sooner to destroy Hotaru. They want to prevent Sailor Saturn from appearing, but the inner senshi would always protest. But now there is nothing for them to do but join forces and stand up against Mistress 9.

However, the senshi are not the only obstacle in Mistress 9's way. The voice of Hotaru is still within her, and trying to get out. She's trying to destroy her from the inside. Although weak, the voice manages to get to her and does destroy her. Tomoe Souichi (Hotaru's father) has also turned into a monster, and is then destroyed as well.

The voice manifests itself in the spirit of Hotaru and appears to Chibi-Usa. She gives her back her ginzuishou and her spirit so she may fight alongside Sailormoon. Mistress 9 is still there, but as an even more terrible monster. The two Sailormoons transform into their super forms... Super Sailormoon and Super Sailorchibimoon. The monster begins to expand rapidly as it rises into the air, and begins to sense Pharaoh 90. It then crashes down and destroys many things in the area, allowing Pharaoh 90 to take over.

Mistress 9 in the anime is also destroyed by the voice of Hotaru. The black star on her forehead breaks to reveal the symbol for Saturn, and then she turns to dust. During the Silver Millenium, the soldiers of the outer planets were told that their talisman must never be brought together. If that would happen, there would be death and ruin in the world. But their talisman were unified, and they watched helplessly as the Soldier of Destruction, Death, and Silence, Sailor Saturn, was summoned. All was destroyed as she brought her Silence Glaive down on the world. In order to prevent this from happening once more, the soldiers of the outer planets remain distant. But they are united again, and unleash the powers of Sailor Saturn upon the world. No matter how hard they tried to prevent it, she was still released. Sailor Saturn has the power to end the world, and that is just what she must do to defeat Pharaoh 90. She assures Sailormoon that with death, there will be rebirth, and unleashes her power. "Death Reborn Revolution." And it is all over... This small, beautiful, fragile creature is the messenger of death. She silences everything. But as she says, there is always rebirth...