Queen Nehelenia, originally Queen Helenia, ruled a kingdom where subjects adored her beauty, fueling intense vanity and a quest for eternal youth. A magic mirror's vision of her future as a haggard crone sparked obsession. This fear manifested physically as Zirconia. To sustain her youth, Nehelenia extracted her subjects' dream mirrors, turning them into Lemures, and established the Dead Moon Circus on her decaying realm, the Dead Moon. Envious of Queen Serenity's Moon Kingdom, Nehelenia—as Queen Serenity's dark counterpart—crashed Princess Serenity's birth celebration. Offered peace, she refused, declared herself the Moon's true ruler, and cursed the Silver Millennium to fall before Princess Serenity could inherit, precipitating its destruction. Queen Serenity sealed her inside a mirror. In the anime, she invaded Elysion to steal the Golden Crystal from Helios, but the crystal rejected her evil, leading to her mirror imprisonment. Millennia later, a solar eclipse weakened the seal, allowing the Dead Moon Circus to escape to Earth. Confined to the mirror, Nehelenia commanded through Zirconia and subordinates like the Amazon Trio and Amazoness Quartet to capture Pegasus (Helios) and seize the Golden Crystal to free her. After Pegasus reverted to Helios and the crystal was taken, Nehelenia emerged, destroying Zirconia. Empowered, she engulfed Earth in darkness but was defeated when the crystal's energy reverted her to an aged, Zirconia-like form. To preserve her beauty, she retreated into the mirror. In the anime's fifth season (*Sailor Stars*), Sailor Galaxia freed Nehelenia to manipulate her into awakening Sailor Saturn. Enraged, Nehelenia shattered her "Black Mirror," infecting humans and imprisoning Mamoru and the Sailor Guardians. After subjecting Usagi to nightmares of her past, Nehelenia received forgiveness instead of hatred. This compassion fulfilled her wish to restart life as a child, and she was reborn in her original kingdom, seeking genuine friendships. In the manga and *Sailor Moon Eternal*, no redemption occurred. Nehelenia brainwashed the future Sailor Quartet into the Amazoness Quartet, corrupted Elysion, and sought the Silver Crystal. Defeated by Eternal Sailor Moon using the combined powers of the Sailor Guardians, she withered into an old crone and disintegrated alongside her mirror. She was later revealed as an incarnation of Chaos. Her abilities centered on curses, dream manipulation, and dark magic, including extracting dream mirrors, corrupting individuals, firing energy blasts, and conjuring spiderweb-like bindings. Her appearance featured long dark hair, pale skin, pointed ears, and elegant attire with a spiderweb-patterned cloak. When defeated or stripped of power, she reverted to an aged, Zirconia-like form.