Magical Ruby is a sentient Kaleidostick forged by Zelretch, the Wizard Marshal and Master of Parallel Worlds. She exhibits a distinctly playful personality marked by mischief and a penchant for trickery. Originally assigned to Rin Tohsaka for the critical mission of gathering dangerous Class Cards in Fuyuki City, Ruby abandoned her partner due to conflicts with her counterpart, Magical Sapphire. Sensing Illyasviel von Einzbern's latent magical potential and her fleeting dreams of becoming a magical girl, Ruby chose Illya as her new partner. She tricked Illya into forming a contract, transforming her into a magical girl against her initial wishes and binding her to the vital task of locating and securing the scattered Class Cards – the mission originally entrusted to Rin. As a Kaleidostick, Ruby grants her user the significant magical power required for transformation and combat. This power enables Illya to access diverse magical girl forms and abilities essential for confronting threats posed by the Class Cards and other adversaries. Ruby often displays a flamboyant and talkative demeanor, providing constant commentary and observations throughout Illya's adventures. Her presence acts as both the source of Illya's power and a catalyst for the conflicts and challenges encountered on her journey as a magical girl.