Yellow Diamond

"Yellow Diamond" was first mentioned, by Jasper, in "The Return".

Jasper & Peridot
She holds some role of authority over them.

Gemology
Learn about the diamond gemstone here. To learn about the metaphysical properties of yellow diamond, click here.

Trivia

 * Both Jasper and Peridot wear uniforms that contain yellow diamonds.
 * This may imply that Yellow diamond is some sort of "general", in other terms, that leads Gems into non-Gem controlled planets.
 * Implied by Ronaldo's deduction of a "Great Diamond Authority", there seem to be more than one "Diamond".