Sailor Galxia is the main villain in the 5-th seasone of Sailor Moon ( Sailor Stars ). She appeares after Queen Neherelinia being healed. Well not excactly, becourse she was the one to free Neherelinia from her mirror:

"I'll brake the mirror, and set you free", - she said.

But anyways. She collects star seeds, and when she would have them all, she would have become the ruler of the universe. But before capturing a planet she has to gather all the True Star Seeds ( Posessed by Sailor senshi ). Thats why she sends her minors ( Sailor Iron Mouse, Aluminum Siren, Lead Crow, and Tin Cat ) on Earth to gather Star Seeds. However Iron Mouse haven't even found one, so Galaxia killed her, Siren found out that Usagi was Sailor Moon, but she was also sentenced to death by Galaxia before she got it. Lead Crow was killed by Tin Cat, and the last one was killed by Galaxia, whe she finally appeared on Earth. Her minors ware also from Sailor Senshi, but defeated and turned evil by Galaxia.

When Galaxia appeared she was attacked by all Sailor Senshi of Earth, and Star Lights. They ware however defeated, all except Moon and Star Lights. Uranus and Neptune acted like turning to Galaxia's side and even killed Saturn and Pluto, but later atacked her. This however had no succes and they both ware also killed.

In the end Galaxia was fighting against Sailor Moon, and had to show her true face. It become clear that Chaos, one defeated by her, took over her body ( However she sent her Star Seed away, which later transformed into Chibi Chibi ). She transformed into a dark creature with huge black wings and fought Sailor Moon, but her craft wasn't enough to defeat Moon's power of love, and finaly Usagi transformed into Neo Queen Serenity healed her, and Galaxia desided to rebuild the Planets destroyed by her. In the end she appeared to be even prettier then when she was evil.