Serena Sheen reigns as Queen of Neathia amid the Gundalian invasion chronicled in *Bakugan: Gundalian Invaders*. As Fabia Sheen's older sister, she shoulders the duty of defending Neathia and its Sacred Orb. Her physical presence features a slender frame, short dark blue hair, turquoise eyes, and pinkish skin, complemented by regal attire: a white dress with robes, a crown, and silver earrings. This attire evolves later into a more intricate design with additional robes.

Her character reflects resilience and strategic acumen. Serena maintains composure under duress, prioritizing civilian safety through evacuations and morale-boosting during attacks. She demonstrates fierce loyalty to her sister Fabia, guiding and shielding her while initially exhibiting caution toward outsiders, including testing potential allies' trustworthiness.

When Gundalia assaults Neathia, Serena activates an antimatter energy shield, later shattered by Emperor Barodius's Bakugan, Dharak. She dispatches Fabia to Earth to enlist the Battle Brawlers' aid while single-handedly coordinating Neathia's defenses. After Gundalian forces breach the planetary shields and besiege her castle, Serena evacuates citizens to underground shelters. Confronting Barodius directly when he demands the Sacred Orb, she defies his ultimatum, declaring he must kill her to claim it. Dan Kuso's intervention halts this standoff as the Sacred Orb teleports them away.

Following Barodius's defeat and absorption by the Sacred Orb, Serena acknowledges the Battle Brawlers' pivotal role in ending the war. She advocates for peace between Neathia and Gundalia, emphasizing lessons in unity. By *Bakugan: Mechtanium Surge*, she transitions from queen to Ambassador of Neathia, continuing diplomatic endeavors. Beyond the anime, Serena appears as a non-playable combatant in *Bakugan Dimensions*, contrasting her non-battling anime portrayal.