Queen Beryl is the commander of the Dark Kingdom as well as the commander of the four Shitenou. During Silver Millennium, she led the invasion forces to conquer the Moon Kingdom. Queen Beryl has long, wavy red hair and red eyes with yellow scleras. She is always shown wearing a long, purple maxi dress, a golden choker with an indigo gem in the center, turquoise earrings, silver bracelets, and a black forehead tiara.

After transforming into Super Beryl, she grew into a much larger form and had green hair and green skin with a jewel on her forehead. Queen Beryl launched an attack on the Moon Kingdom during the end of the Silver Millennium with an army of brainwashed humans, including the Shitennou. She also wanted to unleash the power of the Dark Kingdom upon the universe in the process. The Moon Kingdom was destroyed and many lives were lost. Although Beryl succeeded in destroying the Moon Kingdom, as well as killing Princess Serenity and Prince Endymion, she was thwarted by Queen Serenity, who used her remaining powers to reincarnate all killed by Beryl's forces and seal away the Dark Kingdom. Queen Beryl's goal is to find the Silver Crystal, take over the world, unleash dark energy upon the universe, and reawaken Queen Metalia.

Initially, Beryl attempted to collect human energy for Queen Metalia's revival. Jadeite made several efforts to steal energy from groups of people by forging items with dark energy, only to be thwarted repeatedly by Sailor Moon. By episode 13, Beryl issued Jadeite an ultimatum, that if he failed to destroy the Sailor Guardians, he would be condemned to Eternal Sleep, a horrible punishment involving the victim being permanently frozen in crystal and being flung into an inescapable realm of profound darkness. As Jadeite failed to successfully carry out his final duty, Queen Beryl cast this sentence him and put Nephrite in charge. Nephrite tried to gather energy from one person at a time, but was foiled by Sailor Moon each time and was threatened with the same fate as Jadeite.