They are named after four Asteroids in the Solar System. Their names were Sailor Ceres, Sailor Pallas, Sailor Juno, and Sailor Vesta. They slept in Amazon stones until they were prematurely released by Queen Nehellenia of the Dead Moon Circus. She corrupted them and turned them respectively as CereCere, PallaPalla, JunJun, and VesVes, making the Amazoness Quartet. When they started regaining their memories, Zirconia sealed them back into the stones. After Nehellenia was defeated, Neo-Queen Serenity, at Sailor Saturn's request, healed the stones, freeing the Quartet who were revealed to be Sailor Guardians.
During the Stars arc, Sailor Chibi Moon, along with her four Asteroid Sailor Guardians went back to the past to fight. When Sailor Moon jumped into the Galaxy Cauldron, Sailor Cosmos returned the Sailor Quartet to slumber to be awakened in their proper time in the 30th Century.
To be added...
- The Sailor Quartet were led by Sailor Ceres.
- The Amazoness Quartet appeared in the 4th season of the first anime but they weren’t revealed to be Sailor Guardians.