The fusion of Sun Diamond and Moon Diamond. Eclipse is mysterious and aloof with a sly and mischievous side. She is almost never seen unfused, only doing so under certain circumstances. Eclipse has a soft spot for defective, off-color, and corrupted gems. She holds these "imperfect" gems close to her, along with humans and gem hybrids.

While Sun and Moon are dedicated to each other, they as a whole, and by extension Eclipse as well, wouldn't mind adding another partner to their relationship as well. However, Eclipse is very picky when it comes to a potential romantic partner, as both her components need to agree on a partner.