Neflite received it from the stars in Episode 19, Molly's Folly, to track down the Imperium Silver Crystal. It reacted to Molly because she was in love with him. Zoycite's monster Yasha thought it was the silver crystal. When Zoycite found out that Neflite was in love with Molly, she sent Housenka, Grape, and Suzuran to kidnap Molly, kill Neflite, and take the Star Crystal. They told him to give them the star crystal, but he beat them up and escaped with it and Molly. However, when Housenka killed Neflite, Zoycite took the crystal.
Afterward, Zoycite used the Star Crystal as a homing crystal to track down the seven Rainbow Crystal carriers so she could extract their rainbow crystals and awaken the Seven Shadows within them.
In Episode 37, Tuxedo Unmasked, Prince Darien, now brainwashed by Queen Beryl, used the star crystal to trap the rainbow crystal carriers so Beryl could use the powers of the Seven Shadows (though all have been destroyed by now) to create the Invincible Shadow. He trapped all but Raye's grandpa inside it, before Sailor Mercury took it from him and smashed it on the ground, destroying it and releasing the crystal carriers.