- Jewel: Obsidian
- Species: Russian Blue
- Gender: Male
- Jewel Power: Superior Dark Magic
- Attribute: Magical Black
- Voiced by: Jun Fukuyama
Dian is the main villain of Jewelpet and Leon's partner in Jewelpet Twinkle. He's a grey Maine coon cat with white paws who with Diana, can also use forbidden dark magic, but in a powerful version called Obsidian Eyes Power (オブシディアンアイズパワー?). He wears a black round orb necklace and a black and red cape in Season One. Debuting in Episode 33, He's Diana's older brother, who despises both humans and the Four Great Magicians of Jewel Land on how they see the Jewelpets and somehow lead a rebellion in Jewel Land during early times. In one scene, he used his magic to cause havoc on Earth and turned all the people into stone. Due to his tyranny, the Great Magicians had no choice but to seal him up in his jewel charm form and into an ice prison in the Bermuda Triangle, in which no Jewelpet nor human can enter. He was awakened by Diana by her magic and he started to cause havoc on Earth by using his captured Jewelpets to do his bidding. Unlike Diana, Dian casts his magic to the Jewelpets themselves causing them to turn evil and the only way Rinko can get them back is through the Jewel Games. Dian can also assume his human form under the name Andy (Anagram for Dian) to seduce Rinko for him to obtain the Jewel Stick. In Episode 47, he successfully captured Rinko due to his magic and "proposed" to her for marriage and in Episode 48, he finally got the Jewel Stick from Rinko's grasp. In Episode 49, he successfully defeated the Four Witches, turning them into stone and planned to go to the Human World using his new dark powers.It was believed in Episode 50 that he already absorbed some of the Jewel Stick's powers after Rinko and Akira reclaimed it for her and his form changed to Dark Dian after the dark magic took over his body, making him more powerful and have more disgust in both humans and Jewelpets during the events of Episode 51. His true intention however is to destroy Jewel Land and take over the Earth, while eradicating every human being in the world, out of belief that the world is filled with nothing but lies, and plunge the world into eternal despair and darkness. Dark Dian was defeated in Episode 52 by Rinko, Minami, Aoi and all of the Jewelpet's combined powers which opened his heart to the fact that Jewelpets and Humans must co-exist in harmony and to know he has friends in Jewel Land to accept him and Diana. After that, he and Diana changed their ways for the better.
In Jewelpet Twinkle, he is Leon's Jewelpet Partner, who can't speak at all due to watching Alma make a jewelpet and got hit by the magic causing him to lose his voice until he remebered what happen. He first met Leon several years ago, in front of the gravestone of his pet dog Roger who recently died and told him if Leon wanted to be his partner to ease his sadness wanting to become stronger to protect close ones Leon accepts his offer and the two became inseparable. The main difference between Dian in season 1 and season 2 is that in season 1, Dian is an antagonist (the villan), and in season 2, Dian is a protagonist(the hero). All of the other Jewelpets have pretty much the same role in both seasons (if they appear in both)--they're either a protagonist, a supporting character, or an antagonist. In Jewelpet Sunshine, he is in 3rd Grade Rose Section and TV Star, he was dating with Garnet and Diana has a feelings for him. Dian's birthday is on January 20 and his name is based on the Igneous Rock Obsidian.
Dian wields a black, evil version of the Jewel Stick, which was originally Rinko's. In Episode 50, Akira and Rinko reclaimed the Jewel Stick but all of its powers were gone.