Fabia Sheen, a Neathian princess who ascends to queen after her sister Serena, begins her journey as a Haos-attribute brawler driven by the defense of her homeworld against Gundalian invaders. Her partner, Aranaut—a Bakugan once bonded to her fallen fiancé Jin, former captain of the Neathian Castle Knights—becomes her steadfast ally after she defies Serena’s orders to rescue him from Gundalian experimentation. Though Aranaut retains no memory of Jin’s death at Kazarina’s hands, their partnership solidifies into a resilient force.

In human guise, Fabia dons a white-and-orange robe with blue boots reminiscent of Runo Misaki’s attire, her blue hair and green eyes contrasting her true Neathian form: purple-skinned with luminous green eyes. As a Castle Knight, her combat armor gleams with yellow and silver, underscoring her dual identity as warrior and royal.

Initially distrustful of the Battle Brawlers and fueled by vengeance for Jin, Fabia clashes with allies like Dan Kuso while outmatching foes such as Zenet Surrow through raw strength and tactical precision. Her rigid animosity toward Gundalians softens when former adversaries like Ren Krawler and Nurzak defect, prompting her to test Ren’s loyalty before acknowledging his redemption.

Witnessing Kazarina’s demise and bonding with Lumagrowl over shared loss shifts Fabia’s focus from retribution to empathy. She allies with former enemies on Gundalian missions, balancing skepticism with a newfound willingness to offer second chances.

Crowned queen in *Bakugan: Mechtanium Surge*, Fabia steps back from combat, entrusting Aranaut to Captain Elright. Her reign prioritizes diplomacy over warfare, reflecting her evolution from warrior to strategist committed to peace. This transformation culminates in mentoring allies like Nurzak and reconciling with Ren, emphasizing emotional resilience and alliance-building.

Episodes such as *Forgiveness* and *Redemption* delve into her internal conflicts between duty and grief, while her bond with Neathia’s Sacred Orb and Element highlights her role as guardian of her planet’s survival. Her narrative closes with a resolve to rebuild Neathia, harmonizing her inherited sovereignty with hard-won wisdom from the battlefield.