The kingpin is Zirkonia, ( AKA 'the one with purple skin') who works from the Tokyo-based Dead Moon Circus. He starts off by sending out the Amazon Trio. These are an inexplicably vain, incredibly camp trio of men around Mamoru's age (18-20) who are given a bunch of photos of potential targets, one of which they pick at random (with me so far?) and eventually attack. The purpose of this is to find Pegasus, would you believe, a unicorn living within a Dream-World and with whom only Chibi (Usagi's lesser half) can communicate. To find Pegasus, the Amazon Trio charm their victim into a quiet spot before violently strapping them to a vertical board and summoning their Dream Mirror, which is evidently painful for the unfortunate victim. Once the mirror has been brought out, they look into it to see if Pegasus is in that person's dream, which he never is. This attack method usually relies on charm, so the lads (Tiger and Hawk) are the ones who do the girls over whereas it's Fish-Eye, the transvestite, charms the lads, including Mamoru. Fish-Eye redefines 'camp' and a female voice actress is invariably used in dubs for his part (he does show the other's his chest to prove he's a bloke in one episode, if I remember rightly).
When the Sailors arrive at the scene of an attack, the lazy Trio don't fight themselves but summon a demon of some kind instead and let it settle the unfinished business. Cue a short and uneventful fight (all that ever happens is that they mess around until Moon and Chibi remember to use the new Kaleido Moon-Scope to kill it).
And so it goes on for the Amazon Trio for about 25 episodes- they do the people over, look in their dream mirror and don't find Pegasus. Fish-Eye is the first one who gets bored with the setup and in one episode attacks his arrogant counterpart Hawk-Eye.
They realises that none of them have a 'Dream Mirror' and they ask Zirkonia why. Zirkonia, the charmer, just attacks Fish-Eye when he puts forward the question and tells the Trio to stop thinking too much. Fish eventually trades with Zirkonia the newly discovered location of Pegasus (he's hiding in Chibi's dream) with a ball of energy which the Trio can use to stay as they know are- soulless humans.
The Trio actually end up using this last lot of energy to restore Usagi's dream mirror after it is smashed by one of Zirkonia's demons. Why? Because they cannot defeat this demon themselves (he was sent to kill the Trio and Usagi) and need Sailor Moon's help. Now, no senshi can be expected to function properly without her dream mirror, so what they do is pretty logical. However, after Sailor Moon and Chibi have sent the demon back to the Dead Moon Circus, the Amazon Trio turn back to what they were (before Zirkonia had them transformed): a fish, a hawk and a tiger. Sailor Moon realises what the Trio did for her and calls Pegasus to see what he can do to help. Pegasus shows up and transforms them back into humans, albeit friendlier and complete with dream mirrors. So much for the Amazon Trio, now the Sailors have the Amazon Quartet to tackle.
The Amazon Quartet are, well, different. They are four girls about the Sailor's age who are also after Pegasus. The only difference is that they are (a lot) more powerful than the Trio were, and use billiard balls to smash the dream mirror out of their victims. Even Zirkonia is wary of them, and realises they could beat him if they attacked together.... like the Trio before them, the Quartet have a tendency summon a 'Demon of the Day' to distract the Sailors while they make off having failed (again) to find Pegasus.
All the while, Zirkonia is having to answer to Nehelenia, the spiritual queen who is after Pegasus and who is getting increasingly irritated with the constant delays. She wants the gold crystal embedded in Pegasus' horn to cause trouble. Ho-hum.
Towards the end of the series, Parapara, one of the Amazon Quartet manages to turn Chibi into an adult (again) and Usagi into a kid. This renders Pegasus pretty much useless, because as a woman, Chibi can't get to him anymore. Pegasus comes to Chibi in a dream and tells her that the Dead Moon Circus are starting to infiltrate his Dream World. He also tells her that he was caught by Nehelenia while he was human and only managed to escape through Chibi's dreams (that's some escape route) and taking on the form of a Unicorn.
Pegasus reveals himself to be Helios, guardian of dreams. Aaaaaaaaah. Chibi soon finds a way to break back through into childhood via a metaphysical portal.
I won't go into the details of the conclusion save to say that Nehelenia gets the gold crystal by sawing off Pegasus' horn and uses it to aid the destruction of the Dream World with the Dark Moon. It later turns out that Nehelenia is a evil sister of Queen Serenity, Sailor Moon's mother, thus revealing her to be the heroine's Aunt.
