Queen Beryl is first antagonist of the Sailor Moon series. She leads an evil group called Dark Kingdom (or Negaverse in the English dub). She is responsible for bringing about the fall of the Moon Kingdom and end of the Silver Millenium. Her goal is to absorb the energy from human beings in order to revive the dark entity, Queen Metalia (the Negaforce in the English dub). However, her efforts are constantly thwarted by the Sailor Scouts. She does however have an infatuation for Darien, Serena Tsukino's/Sailor Moon's love interest. Perhaps this is due to Darien being the reincarnation of Prince Endymion, the love life of Princess Serenity (the previous incarnation of Serena).
In the manga, she was once an Earthling who loves Prince Endymion, but seeing as the prince loves Princess Serenity more, she becomes overwhelmed with jealousy and was influenced by Queen Metalia into destroying the Moon Kingdom.