Black Onyx concept

A homeworld gem who seeks ultimate power, but not in the form of ruling. Rather by draining it from the lives of others. One in particular Cinnabar. Despite the charming appearance Onyx is highly dangerous, a parasite in other words. However he still follows after Yellow Diamond, but recently he's done only freelancing. Conquering other gems and taking their very light from them. Black diminishes all color, like white which brings forth color. Cinnabar is something Onyx has never seen before, but what will he do with the gem? Take his power for himself, or something far worse.