Octave is a Daimon Heart Snatcher made by Kaorinite to extract Pure Hearts. She was created when Kaorinite placed a Daimon pod in a violin, and therefore has the appearance of a violin. She has a high-pitched, screechy voice that she uses to attack, and can even use it to form an energy wave. She appeared in Sailor Moon S Episode 4, Bad Harmony.
Octave extracted a Pure Heart from the violinist who played the violin she was created from, however, she was attacked by Sailor Neptune and Sailor Uranus, and Sailor Moon destroyed her with Moon Spiral Heart Attack.
Her name is a play on the musical term octave.