Lupusregina Beta, also known by her full designation Lupusregina Beta, is a werewolf battle maid and a member of the Pleiades Six Stars, the elite combat maid squad that serves as a last line of defense for the Great Tomb of Nazarick. Her name is derived from the Latin words for wolf and queen.

Lupusregina Beta was created by the Supreme Being Beast King Mekongawa, one of the former members of the guild Ainz Ooal Gown. She is a cleric-type character whose class focuses on healing and support magic, though her combat stats are well-balanced, granting her strong offensive capabilities as well. Among the Pleiades, she possesses the highest overall stats and the greatest physical defense and resistance, though she carries a weakness to silver, which inflicts increased damage against her. She wields a distinctive black and silver scepter that serves as both a weapon and a focus for her magic. Her appearance is that of a young woman with a sporty build, brown skin, and long red hair typically tied in two braids. She wears a modified maid uniform with a slit on the left side.

On the surface, Lupusregina Beta presents a cheerful, bright, and outgoing personality. She is sociable and friendly toward humans and can conduct herself as a perfectly polite lady. She enjoys making lewd jokes and has a playful, mischievous demeanor. However, this sunny exterior is a carefully maintained mask that conceals her true nature, which is cruel, sadistic, and cunning. She derives genuine amusement from watching others struggle and suffer, viewing the fragility of life as entertainment. Her fellow Pleiades member Yuri Alpha has noted that Lupusregina can be as sadistic and evil as her sister Solution. During a full moon, her cruel tendencies become even more pronounced. Despite her underlying brutality, she is also noted in supplementary material to have a surprisingly girlish side, liking flowers when not in a state of self-awareness influenced by madness.

Her primary motivation is loyalty to Ainz Ooal Gown, the supreme ruler of Nazarick, whom she serves with genuine devotion. She finds his actions endlessly entertaining and delights in carrying out his orders. Her obedience is absolute, and she will kill or die for him without hesitation. Her loyalty extends to the hierarchy of Nazarick, and she is intelligent enough to understand exactly how far she can push her behavior before crossing a line.

In the story, Lupusregina Beta is assigned the role of overseer and protector of Carne Village, a human settlement that came under Nazarick's sphere of influence. She is tasked by Ainz with observing the villagers and ensuring their safety. She fulfills this duty perfectly, healing the wounded and interacting with the villagers with warmth and friendliness, but she does so out of obedience rather than compassion, finding amusement in their fear and vulnerability. Her presence in Carne Village serves as a subtle demonstration of Nazarick's reach and control.

Her key relationships are primarily with her fellow Pleiades members. She respects Yuri Alpha's authority and defers to her in serious matters. She enjoys teasing her comrades, particularly Narberal Gamma and Solution Epsilon, for her own amusement. Her dynamic energy provides a contrast to the discipline of the squad. Her bond with Ainz is the most significant, as she views him as the most interesting being in the world and radiates delight when praised by him. She also interacts with the homunculus maids of Nazarick, who consider her the friendliest of the battle maids.

Lupusregina Beta's development is primarily revealed through her interactions and assignments. She maintains a consistent dual nature throughout the series, learning to balance her playful exterior with the seriousness of her role as a guardian of Nazarick. Her time in Carne Village deepens her understanding of loyalty and duty, even if her underlying sadism remains unchanged.

Her notable abilities include powerful healing magic such as Greater Heal, Regeneration, and Anti-Poison Heal. She uses Animal Instinct to read the minds of her opponents and Complete Invisibility to vanish without a trace, allowing her to appear and disappear unexpectedly. Her combat style is dynamic and agile, combining rapid physical attacks with magic. As a werewolf, she can transform into her true form, becoming even more ferocious, especially under the light of a full moon. In the web novel, she is noted to walk on all fours in her transformed state. Her balanced stats and combination of healing and combat skills make her a versatile and dangerous opponent.