Regina emerges as the manifestation of darkness from Princess Marie Angelica's divided heart, embodying the part still loving her corrupted father. This division occurred when the terminally ill Princess required the Golden Crown of Wisdom for survival. After her father stole the crown, transforming into King Mercenare, her heart split: the light became Natalie, while Regina, the dark half, returned to King Mercenare. Regina possesses ankle-sweeping blonde hair, typically tied with a red bow. She wears a dark grey dress with red accents, a black jacket, grey arm bands, ankle boots, and a red choker. Under the brainwashing influence of the red Royal Crystal, her eyes glow red, her skin and hair turn pale, and her outfit's red elements shift to purple.

Initially serving as the secondary antagonist and King Mercenare's second-in-command, Regina displays a selfish, vain, and spoiled personality. She treats others as inferiors and reacts petulantly when opposed. She acts irresponsibly, prioritizing amusement over duty and manipulating others, like the Selfish Trio, to get her way. Her primary ability allows her to create Distains by exploiting latent selfishness in others, bypassing the need for overt negative emotions. Her trajectory shifts upon encountering Maya, whom she pursues as a friend while demanding exclusive devotion. Regina isolates Maya from her friends and retaliates with Distains when rejected. Despite her manipulations, these encounters spark genuine curiosity about friendship, leading to vulnerability. After cheating and losing a game against the Glitter Force, she shows visible distress; later, in an ice cave confrontation without brainwashing, her eyes briefly return to their natural blue.

A critical moment arrives when Regina retrieves the red Royal Crystal from a Marie Angelica statue, unintentionally triggering its brainwashing effect and amplifying her aggression. Later, after King Mercenare electrocutes her for associating with the Glitter Force, Maya rescues her. Trapped together in a cavern above magma, Regina questions their relationship. Hearing Maya declare them friends and that her feelings constitute love, Regina sheds a tear. She willingly lets go to save Maya, and a surge of emotion breaks her magical bindings, enabling their escape. Despite this growth, King Mercenare forcibly re-brainwashes her using dark lightning, altering her outfit to purple and black and reinstating her antagonistic role. She battles the Glitter Force until overpowered by Glitter Ace, who nearly purifies her. Injured and retrieved by the Selfish Trio, Regina blames Maya for her suffering, causing Maya distress. King Mercenare then places Regina in a coma-like state for healing.

Regina later reemerges wielding the Spear of Light (Miracle Dragon Glaive), its blade darkening in response to her conflicted emotions, signaling the weapon's allegiance to her. Her origins are fully revealed alongside Natalie: they are opposing halves of Princess Marie Angelica. Though initially siding with her father to conquer Earth, Regina ultimately chooses to save him after Maya's unwavering compassion reaches her. She collaborates with Natalie and Dina (the reborn physical form of Marie Angelica) to purge King Mercenare's corruption, restoring his true self. This act reconciles her dual loyalties—love for her father and bonds with the Glitter Force.

Following these events, Regina transfers to Seashell Bay Middle School and integrates into the group. Though not an official warrior, she operates alongside the team by the series conclusion, signifying her completed redemption. Her personality retains traces of clinginess but reflects a fundamental shift toward friendship and cooperation.