Queen Serenity ruled the Moon Kingdom throughout the Silver Millennium from the Moon Castle, presiding over an era of peace and prosperity. She was mother to Princess Serenity and guardian of the Silver Crystal, the powerful artifact sustaining her realm. Her appearance featured long silvery-white hair styled in odango buns, a white dress adorned with a gold crescent brooch, and a golden crescent moon symbol on her forehead, denoting her royal lineage. This mark represented the Silver Millennium and was shared by Princess Serenity and the moon cats Luna and Artemis. She maintained harmony between the Moon and Earth, delegating planetary protection to Sailor Guardians like Sailor Uranus, Sailor Neptune, and Sailor Pluto, entrusting them with castles. Significant conflict arose with Queen Nehelenia, ruler of the Dead Moon, who coveted eternal youth and envied the Moon Kingdom's tranquility. During a confrontation at Princess Serenity's birth celebration, Queen Serenity confronted and sealed Nehelenia within a mirror using the Silver Crystal's power. Before her imprisonment, Nehelenia cursed the princess and the kingdom, contributing to the Silver Millennium's downfall. The kingdom faced destruction when Queen Metalia and Queen Beryl orchestrated an attack. Facing annihilation, Queen Serenity unleashed the Silver Crystal's full power to banish their enemies and ensure the reincarnation of her daughter, Princess Serenity, the Sailor Guardians, and their allies on Earth. This act drained her life force, resulting in her physical death. Before perishing, she placed her trusted advisors, Luna and Artemis, into stasis to later guide the reincarnated guardians. In *Sailor Moon Eternal*, her legacy directly shapes events through the consequences of her past actions. Queen Nehelenia's enduring resentment over her sealing fuels her campaign against the present-day Sailor Guardians. Flashbacks depict Nehelenia's intrusion at the princess's birth celebration and Queen Serenity using the Silver Crystal to imprison her. This sealing established the curse Nehelenia placed on the princess and kingdom, a curse persisting into the 30th century and connecting to the Dead Moon Circus's assault on Earth. Queen Serenity's spirit occasionally appeared to guide the reincarnated Sailor Guardians, explaining the Moon Kingdom's history during their visit to the lunar ruins and later returning the Silver Crystal to Usagi Tsukino during a crisis. Physically unable to transform into a Sailor Guardian, a trait shared with her future incarnation Neo-Queen Serenity, she wielded authority through the Silver Crystal and strategic oversight as a non-combatant ruler. Her character is defined by sacrificial leadership, establishing the guardians' reincarnation cycle, and the consequences of her confrontation with Nehelenia, which reverberated across millennia.