She resembles a large crab. She has two large claws and six legs. On the top of her head, she has four small horns and in the center is one large spike. She has only one eyeball, and her iris appears to be the gemstone. She is only seen through Ronaldo's night vision camera, therefore the actual color of her shell is unknown. In the palette seen, she appears to be a dark teal color, although she could be orange and white, like her minions. She has two mandibles on her front acting as a mouth.
The Crab Gem Monster resembles Gohma from the Zelda series, particularly in how she seems to use her claws to help protect her eye, which is her weak spot as well as her ability to spawn smaller versions of herself.