(Image credit to Austeen Manalang @fauxteen)
The Gem Queens are a group of off-color, exiled, abandoned or mutated gems that were cast off of Homeworld for their transgression against gem kind. Assembled by the flawed diamond Mother, the Gem Queens are a dangerous mix of powerful but otherwise discarded gems who once served homeward loyally.
Abandoned, the gem queens wondered looking for new purpose and to exact revenge on the Diamonds who abandoned them. United under a common cause, the gem queens now work together to overthrow the Great Diamond Authority and supplant their Mother as the new gem ruler.
Casting off their labels as off-colors, mutated, flawed or throw out gems, they relabeled themselves Queens and intend to not only rule Homeworld but all of their captured planets, including Earth.