Iron Mouse didn't work alone! During and proceeding her attempts to find the true star seed, other members of the Shadow Galactica played a large part in the series. I recommend checking out the links page to see the shrines for these characters, but first here's an overview of who these villains are.
Sailor Galaxia is the lead villain of the Stars series. Although, like all lead "Sailormoon" villains, there are greater forces at work... Legend says that the most powerful Sailor Senshi in existence is Sailor Galaxia. However, even her power wasn't enough to destroy Chaos. Because of that, we have the Galaxia we see during most of the series -- corrupt and vengeful. She aims to collect all of the star seeds in the galaxy, which would result in her having complete control. Her seiyuu is Horie Mitsuko, who's also acted as Hilda ("Saint Seiya"), Kyoko ("Cyber City Oedo 808"), and Sakurako and Kaori ("Esper Mami").
Sailor Aluminum Siren is the Anima Mate to take Iron Mouse's place. She tends to act flighty and eat a lot, but she can be very dangerous to come across when she's doing her job. She's the only Anima Mate who used her attack, "Galactica Tsunami," in the anime as well as the manga. She goes by the name Aya Reiko when not in Senshi form and dresses in a feminine suit reminicent of the early 60's lady's wear. Her seiyuu is the very popular Inoue Kikuko. You've probably heard as Princess Lubiina ("Sailormoon SuperS"), Belldandy ("Oh My Goddess!"), Tendou Kasumi ("Ranma ˝"), Mimori Seira ("Saint Tail"), and many more. ^^
Sailor Lead Crow worked with Aluminum Siren (and later Tin Nyanko) after she took Iron Mouse's place. Crow was Siren's rival for the number one position of the Anima Mates (which she had a lot of trouble believing after seeing Siren in action ^^;). She can be rather ill-tempered but is confident in her work. While undercover looking for possible targets, her alias is Karasuma Akane. Her seiyuu is Suzuka Chiharu, who has also had a guest role in the popular anime series "Detective Conan."
Sailor Tin Nyanko worked with Lead Crow after Aluminum Siren's duties ended. She doesn't mind betraying others if it gets her ahead, which tends to lead to her not being very beloved amongst "Sailormoon" fandom (especially Lead Crow fans ^^;;). Her seiyuu is Ohtani Ikue, another popular actress. You can hear her as Uchouten ("Sailormoon S"), Merle ("Vision of Escaflowne"), Pikachu ("Pokémon"), Himeko and Erika ("Hime-chan no Ribbon"), Yukina ("Nadesico"), and Ruka ("Tenshi ni Narumon!").
Sailor Heavy Metal Papillon, the soul hunter, was an Anima Mate that did not appear in the anime, only in act 49 of the manga. Her appearance was brief, leaving not much to say about her. But I'll try anyway. She got involved in the storyline when Sailor Moon was trying to find Galaxia. On her way, she and the other characters that remained came across a graveyard with many butterflies. These butterflies are the souls of starseeds, hence why Papillon (French for butterfly) is the soul hunter. In the graveyard is a newly dug grave, and Papillon plans to have it be for Sailor Moon. Does she succeed? ...Yeah, that's pretty easy to answer. ^_~;
This pair only appear in the manga of "Stars." Sailor Lethe (right) was from the planet Lethe and was in charge of guarding the river of oblivion, which is just past the entrance gate of Zero Star (home of the Shadow Galactica). Sailor Mnemosyne (left) was from the planet Mnemosyne and would guard the river of memory. Lethe is the more tough of two, having no problem killing others and attacking Sailor Moon with "Galactica Myosotis Alpestris." However, before Lethe can finish her off, Mnemosyne stopped her and saved Sailor Moon and the others with her. Because they allied themselves with Sailor Moon, however, their lives were cut short by Sailors Chi and Phi.
Sailors Chi (left) and Phi (right), the Star Gardeners, are another pair of manga-only Senshi. Of all of the minor villains in the series, they were two of the most successful. They were the classic bad guys, merciless and killed those who weren't their allies. Because of this, they're not very popular in fandom, as you can probably imagine. Their status in the Shadow Galactica was a step above the Anima Mates, taking responsibility for their actions while appearing before Galaxia. Phi uses an attack name once while facing off with Sailor Moon, "Galactica Plants Blizzard."