Lucy Diamond is the leader of the kingdom's mage corps and the head of the magician academy in the series. She appears as a young girl around ten years old, with long golden hair, pale skin, and a doll-like face, but this appearance is maintained by magic that hides her true age, which is actually far older than the protagonist Beryl Gardnant. Despite her childish look, she speaks with the wisdom and authority of someone who has lived for many decades. Her personality is playful and mischievous; she enjoys teasing others, especially Beryl, whom she finds endlessly entertaining. At the same time, she is dependable and carries her responsibilities as the supreme commander of the mages with confidence. Her motivations stem from a deep curiosity and a relentless drive to master magic. She once lost to a legendary sword master in the past, and that defeat fuels her interest in Beryl, whose swordsmanship reminds her of that earlier encounter. She approaches him not out of hostility but out of a desire to test the limits of her magic and to find someone who can stand as an equal partner. In the story, Lucy Diamond serves as a key liaison between Beryl and the wider magical and political world, opening doors to the mage academy, the royal court, and other institutions. She is the magic teacher of Picell, one of Beryl's disciples, and she entrusts Beryl with training Picell in swordsmanship. She also acts as a protector and guardian figure to the street child Mui, providing her with a home and enrollment in the academy. Her relationship with Beryl evolves from cautious respect to a warm, mutual reliance built on trust and shared goals. Over the course of the narrative, Lucy's playful exterior occasionally gives way to moments of gravitas when she must defend the kingdom or guide younger mages. Her personal development is subtle but meaningful: she learns to rely on others and to see Beryl not just as a curiosity but as a true friend and colleague. In terms of abilities, Lucy is the most powerful mage in the kingdom, known as a living magical weapon by the state. She has mastered a vast array of spells, including fire, ice, lightning, rock, and gravity manipulation, and she can compress space itself. She is capable of healing, magical body enhancement, and mental magic that can impose or remove conditions on a target's consciousness. Her most notable skill is her ability to chant and combine three different spells simultaneously, creating effects that normal mages cannot replicate. She can also form humanoid constructs out of fire, water, or earth and control them precisely. Her power is so great that when she fought Beryl in a direct battle, she was able to match him blow for blow, despite their different disciplines, and she remains one of the very few characters who can contend with him on equal footing.