She is the tenth and last of the Sailor Guardians of the long gone Moon Kingdom to be introduced, possessing immensely strong dark powers associated with silence and ruin, nothingness and the void, destruction and death, annihilation and rebirth.

Prior to the main events of Sailor Moon, when Hotaru was eight years old, she lived with her parents in Tokyo's Sankakusu District when a freak storm occurred causing a fire that killed her mother Keiko and left her on the verge of death herself.

Hotaru is also revealed to be the reincarnation of Sailor Saturn who was responsible for destroying the last remnants of the fallen Moon Kingdom Silver Millenium so it can begin anew of Earth.

This fact and her power made her feared by the Outer Guardians as they initially intended to kill Hotaru and seal her soul before she could awaken and destroy Earth.

She then drives Pharaoh 90 to his domain while sacrificing herself to ensure he remains trapped, though Sailor Moon's restoration brings Hotaru back to Earth as an infant.

With her father dead, Hotaru becomes the adopted daughter of Haruka Tenoh, Michiru Kaioh and Setsuna Meioh as the four of them reside at an Empire Victorian House.

[3] As a character with special powers, ever evolving transformations and a long lifetime virtually spanning between the Silver Millennium era and the 30th century, Hotaru gains multiple aspects and aliases from both her separate personalities (until Mistress 9 is fully expelled) as the series progresses.

Sailor Saturn wears a dark blue-violet uniform with a pale maroon bow in the front of her chest with a silver crystalline brooch and in the back of her miniskirt.

In her past life, Sailor Saturn lived far from Silver Millennium and only appears during a crisis with the Three Talismans of her fellow Outer Guardians serving as keys to summon her once the items were brought together.

In the first anime, retaining her sense and defying the extraterrestrial parasite, like in the manga and its 2014-2023 reboot, Hotaru fully awakened, as one with Sailor Saturn herself, and ultimately destroyed Mistress 9's persona at the cost of her physical self.

In the revision, her identity as Hotaru is stated plainly, and she awakens on-stage as Saturn, after being saved by the other Sailor Guardians and appears transformed moments later.

Some of these are portrayed only in the third story arc, such as her past life existing as a secondary personality that unconsciously transmits visions to the other Sailor Guardians of incoming disasters that would lead to her eventual awakening.

Prior to her awakening, Hotaru displayed the ability to involuntarily create force-fields and energy beams whenever in danger and heal minor flesh wounds.

Due to the destructive nature of her powers, Hotaru would be reborn as an infant immediately upon fulfilling her task as Sailor Saturn in an event that ends with her demise.

"[15] Calling herself a "harbinger of death", referred by others as the Forbidden Guardian, Saturn's primary role is execute total annihilation and is normally summoned as a final resort when all hope is lost.

Such an example is Saturn wiping out what remained of Silver Millennium after Metaria destroyed most of it, which made the Outer Guardians greatly fear her as they did not fully understand her purpose at the time.

[18] When first awakened during the Mugen Academy incident, a result of Sailor Moon's apparent demise, Saturn's first act was deeming Earth beyond salvation while fatally weakening Master Pharaoh 90 with her "Death Reborn Revolution.

[19] But when Sailor Moon remerges alive and unharmed, Saturn renounces her intent of destroying Earth and deliberately allows herself to be sealed away in Master Pharaoh 90's dimension while he is escaping.

In the original anime's third season, Saturn will die from using the attack, only to be saved by Super Sailor Moon at the last moment as she obliterated Pharaoh 90 from existence with incredibly powerful bursts of purple destructive energy.

When Sailor Saturn returns near the end of the fourth story arc (which actually overflows into the beginning of the fifth season), a couple more attacks are introduced.

[24] In the stage musicals, Hotaru has been played by twelve actresses: Keiko Takeda, Chihiro Imai, Asami Sanpei, Mao Mita, Mario Tomioka, Ayami Kakiuchi, Ruria Nakamura, Yui Iizuka, Eriko Funakoshi, Karin Takahashi, Mirai, and Yuuka Ide.