This is what we found on Wikipedia regarding the Dream Circus:

The Dead Moon Circus (デッドムーンサーカス, Deddo Mūn Sākasu) are a group of fictional characters from the Sailor Moon manga series created by Naoko Takeuchi. They serve as the main antagonists of the fourth arc, called Dream in the manga, Sailor Moon SuperS in its first anime adaptation, and Sailor Moon Eternal in the second anime adaptation. They are first introduced in chapter #39 "Dream 1 – Eclipse Dream", originally published in Japan on September 6, 1995. In the original English dubbed anime by Cloverway, they are called the "Dark Moon Circus".

The Dead Moon Circus is led by the twisted Zirconia, in command by the absence of the dark Queen Nehelenia who is trapped within a mirror. Zirconia is searching for the legendary Golden Crystal, which will allow Nehelenia to break free of her entrapment and take over the Earth. They are the only group of villains with two subordinate groups: the Amazon Trio and the Amazoness Quartet.