She impersonated Amy's computer school teacher and gave the class disks charged with dark energy. When Amy forgot her disk, and Luna found it to be charged with dark energy, she thought Amy was working for the Negaverse, but when Serena used disguise power to stop her, Garoben revealed her true identity. Serena transformed into Sailor Moon. After asking her a tough multiplication question (355 x 268), she threw razor sharp test papers at her when she did not answer. She then attempted to brainwash Amy.
At that moment, the Mercury symbol appeared on her forehead, so Luna gave her a transformation pen and she transformed into Sailor Mercury just when Garoben was turning her arm into an axe in an attempt to kill her. Sailor Mercury used Mercury Bubbles Blast, which made Garoben cold and prevented her from seeing Sailor Mercury or Sailor Moon. After unsuccessfully attempting to attack Sailor Mercury with her axe arm, she was destroyed by Sailor Moon with Moon Tiara Magic.