TV-Series
Description
The character referred to as Ottavia is a localized name for Hotaru Tomoe, the civilian identity of Sailor Saturn in Sailor Moon S. Sailor Saturn is the tenth and final Sailor Guardian introduced in the series, the reincarnation of the Princess of Saturn, and is known by the titles Guardian of Silence, Guardian of Destruction, and Guardian of Ruin and Rebirth. Unlike the other Sailor Guardians, whose human identities and guardian spirits are separate beings, Hotaru and Sailor Saturn share the same soul and body; the guardian's spirit resides deep within the frail twelve-year-old girl, and the two personalities eventually merge into one.

When Hotaru was eight years old, a freak storm and fire in her father's genetic engineering laboratory killed her mother Keiko and left Hotaru on the verge of death. Her father, Professor Souichi Tomoe, made a bargain to save her life, and in the process Hotaru became the host of the Daimon Mistress 9, an entity that caused her to suffer seizures, fainting spells, memory loss, and occasional violent episodes she could not remember. Because of this, she was ostracized and feared by her classmates and grew up isolated, with no friends until she met Chibiusa. In the manga version, her body was also altered into a cyborg as part of the same bargain.

Hotaru is shy, gentle, socially awkward, and physically frail, and she was described by the series creator as delicate, quiet, precocious, and expressionless. She is intellectually gifted and enjoys reading, and although she is distant with those who do not understand her, she shows great warmth and devotion to the people she trusts. As Sailor Saturn, her demeanor becomes noticeably more stoic, serious, and detached, reflecting her role as a being tied to silence, death, and destruction, though this severity softens after her spirit merges with Hotaru's.

Sailor Saturn's power is tied to ruin and rebirth: she is able to annihilate a planet, an entire solar system, or reset its evolution. Her destructive force complements the restorative power of Sailor Moon, and in the past life of the Silver Millennium she was the one who destroyed the ruined remnants of the fallen Moon Kingdom so that a new era could begin. Because of this, the Outer Guardians Sailor Uranus, Sailor Neptune, and Sailor Pluto feared her awakening and initially intended to kill Hotaru to prevent the destruction she could bring. In the climax of Sailor Moon S, Hotaru loses her body to Mistress 9, who steals Chibiusa's Silver Crystal to fully manifest and summon the entity Pharaoh 90. When Sailor Moon appears to perish, Hotaru awakens as Sailor Saturn and prepares to destroy Earth along with Pharaoh 90 so that the world can be reborn. Seeing that Sailor Moon is still alive, she decides that destruction is not necessary and instead uses her power to drive Pharaoh 90 back into his own dimension, sacrificing her own life to ensure he remains trapped. Sailor Moon's power then restores Hotaru as an infant so she can live a new life free of Mistress 9's influence.

Her most important relationship is with Chibiusa, who becomes her first true friend and remains devoted to her despite the warnings of others; Hotaru even uses her healing ability to mend Chibiusa's injuries, an act that leaves her weakened. Her father Souichi Tomoe survives the events of the anime and cares for her after her rebirth, while in the manga and Crystal versions she is taken in by Haruka Tenou, Michiru Kaiou, and Setsuna Meiou, whom she comes to call her parents. Her bond with Sailor Moon is also central, as Sailor Moon's survival and willingness to save her are what lead the character to choose rebirth over destruction.

Across the series her age fluctuates: she is introduced at twelve, reborn as an infant at the end of Sailor Moon S, develops into a child of about four or five, and later returns to her proper age after a metaphysical awakening in which Sailor Saturn appears before her. In later stories she reawakens to fight Queen Nehellenia, foresees great peril, awakens Eternal Sailor Moon for the first time, and channels her power to raise the other Outer Guardians to higher levels of strength, further showing her connection to rebirth and renewal.

Sailor Saturn wields the Silence Glaive, a weapon capable of destroying a world or worlds with a single swing, and commands powers associated with silence, darkness, nothingness, destruction, death, and rebirth. She can generate protective force fields, launch destructive energy attacks with her glaive, heal minor wounds, and receive visions of the near future. In the anime she is also notable as the only Solar System Sailor Guardian without a transformation sequence and the only one who never fights an ordinary monster of the week, as her power is reserved for endings and new beginnings.