Queen Beryl is the leader of the Dark Kingdom and the principal antagonist of the first season of the anime Sailor Moon. Her name is derived from the mineral beryl, and she is presented as a striking figure with long, wavy red hair and a purple gown, often shown carrying a staff topped with a dark crystal orb. Her history reaches back to the ancient age of the Silver Millennium, when she was an ordinary woman named Beryl living on Earth as a shrine maiden in the kingdom of Earth. She fell in love with Prince Endymion, but her love was not returned, and when she discovered that Endymion had given his heart to Princess Serenity of the Moon Kingdom, her jealousy and resentment took hold of her. The evil entity known as Queen Metaria, born from the darkness of the sun, exploited those feelings and corrupted her, granting her power in exchange for her loyalty. Under Metaria's influence, Beryl led the forces that invaded the Moon Kingdom, and it was she who killed Endymion while he shielded Princess Serenity, an act that drove Serenity to take her own life. Beryl herself was slain by Sailor Venus during that distant war, and Queen Serenity sealed Metaria away before sending the fallen peoples of Earth and the Moon to be reborn in a future age.

In the twentieth century, Beryl was reborn as a human scholar. While conducting research in the Arctic at a location known as D-Point, she came into contact with the imprisoned Queen Metaria and was again seized and transformed, becoming the Queen of the Dark Kingdom. From her icy stronghold, she commands the Four Kings of Heaven, Jadeite, Nephrite, Zoisite, and Kunzite, dispatching them and their demon servants to Tokyo to drain the life energy from humans. That harvested energy is delivered to Beryl and channeled through her dark crystal into Metaria, whose eventual release is the central goal of her campaign. At the same time, she seeks the Moon Princess and the legendary Silver Crystal, believing that obtaining them will secure her victory over the Sailor Guardians and her dominance over the world.

In the anime, Beryl is portrayed as cunning, authoritative, and openly cruel. She listens to the reports of her generals but ultimately depends on her own judgment, and she regards the people around her as tools to be spent freely, even killing one of her own officers, Zoisite, with her own hands when it suits her purposes. The defining element of her personality is her obsessive and unrequited love for Endymion, which persists into the present day and is directed at his reincarnation, Mamoru Chiba. She is deeply jealous of Princess Serenity, whose modern identity is Usagi Tsukino, otherwise known as Sailor Moon, and much of her malice toward the Sailor Guardians is colored by that rivalry. Her love for Endymion is also her weakness, because she can force Mamoru's obedience but cannot make him love her in return.

Her role in the story is that of the mastermind behind the Dark Kingdom's attacks for the majority of the season. While her generals carry out schemes to collect energy in the human world, she remains in the shadows, directing their efforts and punishing their failures. As her subordinates fall one by one, she becomes more directly involved, and her obsession leads her to kidnap Mamoru and brainwash him into a dark servant who is meant to love her and to destroy Usagi. When Mamoru breaks free of her control and wounds her, she is left desperate and defeated. Begging Metaria for more power, she is consumed by the entity and transformed into an enhanced monstrous form, Super Beryl, which serves as Metaria's vessel for the destruction of the world. Sailor Moon, having awakened to her identity as Princess Serenity, destroys Beryl and Metaria together using the combined power of the Silver Crystal and the Moon Stick, bringing the conflict to an end.

Her development across the season follows a path of increasing desperation. She begins as a distant schemer, confident in her generals and her own authority, but each loss narrows her options and feeds her frustration. Her attempt to reclaim Endymion through possession rather than love fails completely, and her final decision to surrender herself to Metaria represents the end of her independent will, since she is absorbed into the very power she sought to control. The tragedy of her character lies in the fact that her original humanity was shaped by genuine, if unreturned, love, and that emotion was twisted by Metaria into jealousy, hatred, and ruin, leaving her to be remembered less as a sympathetic figure and more as someone broken by her own desires.

Queen Beryl possesses considerable magical power, much of which she uses to receive and transfer the life energy collected by her subordinates, feeding it to Metaria. She is able to draw upon Metaria's power to reinforce herself and her forces, and she maintains the ability to communicate with the entity across the darkness that sustains her. She can corrupt and control the minds of others, as demonstrated by her successful brainwashing of Mamoru, and she commands armies of demons that act as her eyes, ears, and weapons in the human world. She wields a staff bearing a black crystal orb that stores gathered energy and serves as the focus of her magic, and she is capable of unleashing destructive attacks directly, as shown when she executes one of her own generals. In her merged form with Metaria, she gains vastly increased strength and a monstrous appearance, becoming a true physical threat rather than a distant commander. Despite her power, her magic is consistently countered by the purifying light of the Sailor Guardians, and her ultimate defeat comes at the hands of Sailor Moon when the power of the Silver Crystal is used against her in full.