Hotaru Tomoe, civilian identity of Sailor Saturn, bears a name signifying "firefly sprouting from Earth," echoing her ties to destruction and rebirth within Japanese mythology. Daughter of Professor Souichi Tomoe and Keiko Tomoe, her childhood shattered when a laboratory accident killed her mother and left her fatally wounded. Her father saved her using forbidden research, reconstructing her as a cyborg and unknowingly implanting the parasitic Daimon Mistress 9 from the Tau Star System. This caused chronic health problems, memory loss, and violent episodes that isolated her at Mugen Academy. Her life shifted upon befriending Chibiusa, who stayed loyal despite Hotaru's condition. When Mistress 9 fully awakened and stole Chibiusa's Pure Heart Crystal/Silver Crystal to summon Pharaoh 90, Hotaru's spirit fought internally to shield her friend. This conflict triggered her awakening as Sailor Saturn, Guardian of Silence and Destruction, expelling Mistress 9 forever. To defeat Pharaoh 90, she prepared to unleash her ultimate power – destroying Earth and herself by lowering her Silence Glaive – but halted upon seeing Sailor Moon alive. She sacrificed herself instead to seal Pharaoh 90 within his dimension, resulting in her rebirth as an infant. Adopted by Haruka Tenoh, Michiru Kaioh, and Setsuna Meioh, the infant Hotaru rapidly aged to childhood during peace. When Queen Nehelenia threatened Earth, the spirit of Sailor Saturn surfaced to restore Hotaru's memories and accelerate her growth to adolescence. Reawakening as Super Sailor Saturn (via "Saturn Crystal Power, Make Up!"), she gifted the Outer Guardians their Sailor Crystals and aided in Nehelenia's defeat. During this battle, she identified the Amazoness Quartet as corrupted future guardians of Chibiusa and protected them until their purification. In the Stars arc, Hotaru attended school with Chibiusa, demonstrating protective loyalty over their friendship. When Shadow Galactica invaded, she and Setsuna Meioh were killed by Sailor Galaxia defending Charon Castle, though later revived at the Galaxy Cauldron. Sailor Saturn's powers focus on annihilation and renewal: her Silence Glaive can obliterate planets to enable rebirth, while secondary abilities include the Silence Wall barrier, Silence Glaive Surprise energy projection, minor injury healing, and distant magic sensing. Her transformations evolved from Sailor Saturn to Super Sailor Saturn (with Saturn Crystal) and Eternal Sailor Saturn, featuring increasingly intricate designs with lavender, dark purple, and star motifs. Historically, she was Princess Saturn of Titan Castle in the Silver Millennium, awakening only after Queen Beryl's attack to destroy the Moon Kingdom with her Silence Glaive. Her personality transformed from a timid, isolated child to a serene yet resolute guardian who accepts her role in the cycle of destruction and creation. Despite trauma, she maintains quiet determination, intellectual curiosity (excelling in history and medicine), and deep devotion to her adoptive family and Chibiusa.