Carbink, the Jewel Pokemon, is a Rock/Fairy type. Diancie, one of the mythical event Pokemon, is a unique version of this Pokemon. Should you get a Carbink, though?
At this point, you probably know that Fairy types are useful in Kalos. You should get one if you don’t have a Fairy type. They can be found in the Reflection Cave, which is right before Shalour City, which is where a gym leader is. Korrina, the gym leader there, uses Fighting types. Unfortunately, that doesn’t make Carbink a Pokemon you should use there, as the earliest it can learn a Fairy type move is level 50. They can be found at level 23 in the Reflection Cave. You can teach it Dazzling Gleam, but you can only get that from defeating Valerie, the sixth gym leader. Korrina is only the third gym leader. Carbink can be a good support though, as it can learn both Reflect and Light Screen. Plus, if you can get Carbink to level 50, you can easily take out Drasna. Something to watch out for is Steel types, as Steel moves are doubly effective against Carbink. So, don’t use this against Wikstrom.
Fun Fact: Diancie is actually a mutated Carbink (Does that mean it can be an X-Man?).