Zirconia appears as an ugly, insectlike old woman with lavender skin. Secondary to Queen Nehellenia, she controls the Amazoness Quartet and the Amazon Trio. Her name is derived from the mineral zirconium dioxide, which is often called zirconia. She first appears in Episode 128 of the anime and Act 34 of the manga. In the English-language adaptation Zirconia's gender was changed from female to male.

In the anime, Zirconia looks the way Nehellenia would look if she were old, and thus she haunts the queen's dreams. Zirconia is the personification of Queen Nehellenia's nightmares, given form to lead the Dead Moon Circus to find Pegasus and carry out the Queen's revenge. She commands the Amazon Trio to go to earth and seek out those with beautiful dreams, who might have the Dream Mirror in which Pegasus is hiding. She uses Zircon, a flying eyeball that usually sits atop her staff, to gather images of those with beautiful dreams, which she gives to the Amazon Trio as their targets. She soon becomes impatient with the Amazon Trio, and allows the Amazoness Quartet to send lemures to kill them. She then sends the Amazoness Quartet to do what the Trio failed to accomplish.

In the manga, the Amazon Quartet calls her baa-san, meaning "grandmother" or "old woman," and she acts as a mediator between them and Nehellenia. Like the other members of the Dead Moon Circus, she doesn't like light, and feels comfortable only in darkness. She speaks to Nehellenia through the mirror, complimenting her often. Little is known about her motivations, but the most important thing to her is to figure out how to make Nehellenia's plans work. Her first mission for the Quartet is to make sure that the circus is a success on Earth, and then taking over everything for the Dead Moon Circus, little by little. She tells them to proceed cautiously when dealing with the Senshi, and lets them know that she will not tolerate a failure. In order to conquer the Earth, she says, they must first destroy the Senshi by filling them with nightmares.