Zirconia

Zirconia is the leader of the Dark Moon Circus, the main antagonist of Sailor Moon Super S, and second only to Queen Nehelenia. He was created from Nehelenia's fear of becoming ugly, and came to exist in the real world when Nehelenia was trapped inside her mirror. He has a pet named Zircon, who has the appearance of an eyeball with wings and a flame, and usually resides on top of his staff, but also takes pictures of the Dark Moon Circus's targets. He also took a tiger, a hawk, and a fish, and used his magic to transform them into human forms called Tiger's Eye, Hawk's Eye, and Fisheye, the Amazon Trio.

At the solar eclipse, Zirconia and the Dark Moon Circus arrives on Earth in an attempt to find Pegasus so Nehelenia could escape her mirror by using his crystal, then rule the world. Zirconia sent the Amazon Trio to extract dream mirrors and look into them to search people's dreams for Pegasus, but they never found him (not even when trying targets that Zirconia himself suggested) and Sailor Moon and Sailor Mini Moon always fought them off.

When Zirconia revealed to them their origins and that they could remain human by taking Pegasus's horn, Fisheye began to question whether or not what they were doing was right, and if Zirconia really intended for them to remain human. When Zirconia decided he didn't need the trio anymore (not telling them this, of course), he sent Hawk's Eye to extract Serena's dream mirror, believing her to be the holder of Pegasus. After Tiger's Eye and Fisheye left, Para Para, one of the Dark Moon Circus's Amazon Quartet, sent a monster named Mr. Magic Pierrot to kill them. The Amazon Trio were all killed in the end, but after Mr. Magic Pierrot was destroyed, Pegasus revived them in human forms.

From here, Zirconia sent the Amazon Quartet, consisting of Besu Besu, Cele Cele, Jun Jun, and Para Para, to search the dream mirrors, now knowing that the dream mirror Pegasus is inside will be gold. However, their many attempts failed, so Nehelenia plunged the world into darkness. When the Sailor Scouts came to stop her and fought off the Amazon Quartet, Nehelenia realized that Rini was the holder of Pegasus, so Zirconia used Zircon to extract her dream mirror. She got it back, but he trapped her inside Nehelenia's mirror. The Amazon Quartet released her to ride Pegasus and take his horn, but Zirconia found out and trapped them in mirrors in another dimension.

After trying to trick the Sailor Scouts with their reflections, Zirconia fought them, and soon teleported the Amazon Quartet there and began to drain their power. However, they crushed their orbs, releasing them from Nehelenia's power and preventing him from absorbing more power. Zirconia retreated, where Nehelenia finally got Pegasus's horn and escaped from the mirror, and by doing so, Zirconia was destroyed, unable to exist in the real world while Nehelenia was outside of her mirror.

Trivia

 * Zirconia was a woman in the Japanese version, an ugly old hag.
 * Zirconia sounds like Yoda.
 * Zirconia (and Zircon) is the only major villain to permanently die in Sailor Moon Super S. All the others (except Nehelenia, who gets sealed inside her mirror) turn good. The only other ones to die are the Amazon Trio, who are revived.