In the Manga she looks a lot like Wiseman. You know, the one you can barely see except for a cape and two hands. Sailor Chaos was the last starseed to be born in the Galaxy Cauldron (where all of the stars/planets/starseeds are made). Instead of it turning into a planet it turned into a sun. (Sailor Chaos=Sailor Sun in a way). She thought she was made to be powerful, and that should could change this 'trashy galaxy' into a better one. Possible ruled by her. She needed four starseeds. Her own, Galaxia's, Moon's, and Kakyuu (spelling?). She split herself into five different 'powers'. They were Queen Metallica, Nemesis, Pharoh 90, and Neherina/Zirconia, and the one that took over Galaxia.
She didn't take over Galaxia. Chaos offered her power that Galaxia accepted, but Chaos possed her.
In the last of the manga, Sailor Moon was able to free Galaxia from Chaos. Moon jumped (sacrificed) into the Galaxy Cauldron (not only setting Galaxia free which kills her), but is able to banish Chaos by summoning the power of the Sailor Crystals. Choas is returned to the hearts of everyone... her 'rightful' place.
~Back to The Chaos Shrine~