Seven Great Youma

In their dormant guise the seven begin as vague, shadowy shapes, but once a Rainbow Crystal is drawn out of its human host, each one snaps into a vivid, monstrous body colored by the person it had been hiding within.

Ranked as the strongest warriors the Dark Kingdom ever fielded, the group played a decisive part in the assault on the Moon Kingdom during the Silver Millennium. Its seven members are Gamecen, tied to the red crystal; Boxy, the orange; Bunbo, the yellow; Veena, the green; Rikoukeidar, the blue; Jiji, the indigo; and Bakene, the violet, together spanning every hue of the rainbow.

When the Dark Kingdom moved against the Moon Kingdom, Queen Serenity locked the seven inside the Silver Crystal, which then split into seven differently colored shards known as the Rainbow Crystals. She sent those shards to Earth together with her daughter Princess Serenity and the royal court, all of them set to be reborn as everyday people.

Generations later, Queen Beryl assigns Zoisite to rouse the monsters and gather the crystals sealed within each host. As the shards come loose one after another, the hosts revert to monstrous form and battle the Guardians, and Sailor Moon's Moon Healing Escalation returns each victim to normal while destroying the creature inside. Beryl afterward turns Prince Endymion against the hosts, aiming to fuse them into a single overwhelming monster, but Sailor Mercury shatters the crystal imprisoning the remaining six before he can finish.