Black Lady was the result of Chibi Usa's exposure to the dark power of Wise Man. Wise Man tricked Chibi Usa into thinking that she was totally unloved. He altered her memories and so the little girl was filled with anger and hatred. She absorbed the dark power and turned into an older version of herself, becoming Black Lady, Queen of Darkness.

Black Lady was determined to destroy everything and everyone because she was angry at the world for not loving her. She was the most powerful of Wise Man's minions, and was quite merciless. Black Lady used Luna P in combination with the dark power for a variety of attacks.

Black Lady eventually realised the truth that she is loved and reverted back to being Chibi Usa, who helped Sailor Moon / Neo-Queen Serenity defeat Wise Man in the end.