Sailor Galaxia originated alone on a small planet she deemed garbage. She wandered alone until the day her powers came to her. But she had no purpose for herself, and felt that the mere role of a Sailor Senshi did not satisfy her; she craved something and she thought that was power. She left her planet in search of another place which she could call home. During her travels she came acroos Chaos, in the form of Wiseman, who showed Galaxia what she was looking for—the Galaxy Cauldron. She discovered that in order for her to gain control of the Galaxy Cauldron she had to gather all the Sailor Crystals of all the Sailor Soldiers of the galaxy. Those powers combined together with that of Sailor Moon would give her the power to kill Chaos and rule the galaxy.
She then created Shadow Galactica and traveled to planet after planet, destroying them and stealing the star-seeds of their guardian Sailor Soldiers. In her first conquest on Earth, she stole Mamoru's golden star seed right in front of Usagi's eyes; and after that, she and her minions stole the life force of each of the Sailor Soldiers on Earth until only Sailor Moon, Chibichibi and the Sailor Quartet were left. At the Galaxy Cauldron, Galaxia proceeded to battle them, until Chaos tried to kill Galaxia by blasting her off a cliff. Sailor Moon rescued her from falling over the cliff into the cauldron, and Galaxia finally realized that what she had always really wanted was love, not power. By accepting Sailor Moon's offer of friendship, the bracelets which supplied Galaxia with life and power shattered, and she died with a smile on her face.