Emerald is a new member of the Crystal Gems. Originally she served under Yellow Diamond and was just underneath Jasper in the ranks.
When coming to Earth in search of Moonstone, Emerald spied on the Crystal Gems and was surprised at how happy they all were. She had never known happiness before (Emerald didn't know what to call it, and had never even seen a smile before, so she first referred to happiness as "mouth contortions"), but somehow knew she wanted to feel something other than unquestionable loyalty. So Emerald burst into the house and begged for the Crystal Gems to teach her their "mouth contortions."
Unlike Moonstone, Emerald was well trained in fighting. Her weapon of choice is actual throwing stars.
Emerald is my OC.