Dark Kingdom

The Dark Kingdom is less a single enemy than a hierarchy of them. Queen Metalia reigns as its supreme power, Queen Beryl serves as her second and public commander, and beneath them stand the Shitennou, the Four Kings of Heaven, made up of Jadeite, Nephrite, Zoisite, and Kunzite. Rank-and-file Youma carry out the assignments, and in the anime a set of Seven Great Youma along with the DD Girls fill out the ranks.

The organization holes up in a cavern at D-Point near the North Pole. It is the only villain group to feature in every version of the franchise, showing up across the manga, the anime, the live-action series, and Crystal, and it is always the first enemy the Guardians face. The DIC English dub renamed it the Negaverse.

At its core the group exists to blanket the world in darkness. Its practical objective is amassing human energy, and later the Silver Crystal, to revive and empower Queen Metalia so the Kingdom can seize the universe. In the Codename: Sailor V manga it even spins off a sub-division, the Dark Agency, which chases the same energy-gathering goal beyond Japan's borders until Sailor V dismantles it.

The Kingdom's roots reach back to the Silver Millennium, when Beryl led an assault that toppled the Moon Kingdom and killed Princess Serenity, leaning on an army of brainwashed humans and the corrupted Four Kings. Queen Serenity gave her life to seal the enemy away and reincarnate her people on Earth. In the present a reborn Beryl reawakens the Kingdom, bases it at D-Point, and turns Endymion's former knights into her generals.

Across the anime's first arc, Beryl cycles through commanders as the Guardians thwart each energy-gathering scheme. Jadeite is sealed in eternal sleep after repeated failure, Nephrite is slain by Zoisite once he falls for Naru Osaka, and Zoisite and Kunzite pivot to hunting the Rainbow Crystals that hide the Seven Great Youma. Once the shards reunite into the Silver Crystal, the Guardians recover their past-life memories. Beryl eventually captures and brainwashes Mamoru, but after Kunzite falls, Sailor Moon reaches D-Point, frees Endymion, and confronts Super Beryl once Metalia merges with the queen. Rising as Princess Serenity, she destroys them both and ends the Dark Kingdom for good.