It's based on my idea that there're more than four diamonds. My characters are Black Diamond, two pearls, and a quartz; Black Diamond is a smaller diamond, and not as respected as her peers. After a political disagreement with Yellow Diamond, Black Diamond's two friends/companions were killed along with their guards. One of their pearls was poofed in the fight, and the other pearl saved her from being shattered and ran to Black Diamond for help; when another assassin came for Black Diamond, she, the two pearls, and her guard Smokey Quartz escaped.
If someone wants to RP the canon gems, the group can go to earth, but if not, we can figure out a plot that doesn't involve those characters.