Diancie is a distinctly feminine fairy-like creature with a gray rocky body embedded with bright pink crystals and gemstones. This Legendary Pokémon is the result of a mutated Carbink. Diancie wears a white cloak-like garment with long white sleeves from which its tiny gray hands protrude. Diancie has a golden collar around its neck, a pink diamond on its chest, and a crown-like formation of pink gems upon its head. It has bright red eyes and small pointed ears. The bottom of its body is composed of a large chunk of rock with a pink crystal embedded in its side.
Diancie possesses a Mega Evolution. Mega Diancie wears a much longer white cloak; attached to its cloak are long white streamer-like ribbons with small pink diamonds dangling from the ends. Mega Diancie's crystal headdress becomes distinctly larger and more extravagant, and the large diamond atop its head changes its shape from round to slightly heart-shaped. The underside of Mega Diancie's body is composed of many large pink crystals, and it has small golden feet. It has golden rings around its neck and waist, and its long thin gray arms can be seen, as it no longer has sleeves.
Diancie is able to create diamonds by compressing the carbon in the atmosphere between its hands. It is the only Pokémon able to learn the move Diamond Storm.