Emerald took over Rubbeus's position after his fiery death in the UFO. She was extremely vain. She believed she was the most beautiful woman in existence. She also had a maniacal laugh that drove everyone crazy... even Prince Diamond would tell her to shut up. Emerald was deeply infatuated with Prince Diamond, and was jealous of his attraction to Neo-Queen Serenity.
Emerald had a different approach altogether. She planned to open the Black Gate so that the Black Moon Clan could use the Black Crystal to destroy the Earth. She would do this by placing dark crystal figurines all over negative energy points in Tokyo. These figurines would absorb negative energy. After the figurines were all in place, the Black Gate would open.
Emerald would disguise herself as a human in order to place the figurines in the right places. She also summoned demons to do her bidding.
In the end, Wise Man deceives Emerald and tells her she would become the Queen of the Black Moon and rule with Diamond. Wise Man gives her a black crystal tiara which she wears, knowing full well that Emerald would be doomed by it. Emerald then turns into a powerful dragon. Sailor Moon manages to defeat the dragon, and Emerald reverts back to herself. She is then sucked into oblivion crying out Prince Diamond's name...
