Fabia Sheen (ファビア・シーン, Fabia Shīn?), now known as Queen Fabia, is the former princess of Neathia and was the Haos Brawler for the Battle Brawlers in Bakugan: Gundalian Invaders. In Bakugan: Mechtanium Surge, she has become the current queen after her older sister Serena Sheen stepped down her position to become the ambassador.

Her outfit in Gundalian Invaders, in her human disguise, is a white and orange robe with a yellow, orange and white robe with rings and white and blue boots (Similar to Runo Misaki's Bakugan Battle Brawlers: New Vestroia outfit). She also has pink earrings. She has navy blue hair which are mostly cover an portion of her face left side and green eyes. Her outfit in Mechtanium Surge is similar to the robes her sister wore during her time as Queen.

When she became a Castle Knight, she wore a high-collared form-fitting combat armor similar to a stormtrooper's armor. It was trimmed in yellow and silver and had blue markings down the sides. She also had a white skirt while in her knight attire.

As a Neathian, she looks like her sister and her skin is a shade of purple and has big green round eyes.

She is the younger sister of Serena Sheen, the previous Neathian Queen. Fabia's reason for brawling is to liberate her planet from the Gundalians. She was also the fiancée of the former commander of the Castle Knights, Jin, who was killed during a battle between him and Kazarina. Aranaut, Jin's Bakugan, then becomes her own.

She seems to have the same kind of love for freedom, justice and initiative to act as Mira does. She has considerable physical strength, throwing Dan over her shoulder twice in episode 3 and once in episode 10, when Zenet tried to take her hostage. Those incidents may prove Ren Krawler's statement about the Neathians' specialty at close combat, although most of what Ren said was a lie to put down the Neathians.

After she was crowned as the new Neathian Queen in Bakugan: Mechtanium Surge, she gives Aranaut to Captain Elright, thus giving up her status as a Brawler.

Fabia is a grateful Neathian; she genuinely loved her late fiancé, Jin. After his death at the hands of Kazarina, she disobeyed her sister Serena Sheen's orders and goes to Gundalia to rescue Aranaut.

Since then, she developed a vengeful nature towards Gundalians believing them to be all hostile and will not rest until they are defeated. However, she eventually trusted and befriended Ren Krawler, his team (except for Sid), and Nurzak after she realized they were all betrayed by Barodius. She also sympathized with Lumagrowl once Kazarina suffered the same fate as her late fiancé.