The Black Ruby was a dark magical gem that had the ability to empower its magical users. It was present within the ruins on Etheria where it was recovered by Horde Troopers who brought it to Shadow Weaver. With its power, her magic was greatly amplified that allowed her to darken the sky around the Whispering Woods. This was with the hopes of killing the magical forest thus defeating the Great Rebellion. Hordak ultimately surrendered the gem to She-Ra in exchange for her to take Perfuma away from the Fright Zone.