Magical Sapphire is a sentient Kaleidostick mystic code designed to transform users into Magical Girls. Originally assigned to Luviagelita Edelfelt, Sapphire abandoned that contract alongside her counterpart Magical Ruby due to Edelfelt's constant quarreling with Rin Tohsaka jeopardizing their mission. She subsequently formed a new contract with Miyu Edelfelt, becoming her partner.

Visually, Sapphire resembles a magical girl wand featuring a six-pointed yellow star within a ring flanked by two small blue beads. She possesses two pairs of butterfly-like wings: larger upper wings are blue with white spots, while smaller lower wings are black with jagged ends. A blue retractable handle with a white top and a white brush completes her form; the handle retracts when inactive and not wielded, leaving only the winged star head.

Personality-wise, Sapphire exhibits a more mature, formal, and duty-oriented demeanor compared to her sister Ruby. She approaches her responsibilities seriously, adheres strictly to orders, and avoids frivolous behavior. This straightforwardness can render her vulnerable to Ruby's excessive teasing or scheming. Despite her formal exterior, Sapphire demonstrates deep loyalty and care toward those she accepts as masters, extending concern to individuals important to her master. Conversely, she can display formal rudeness toward those she deems unworthy.

Sapphire's core abilities mirror Ruby's, granting her wielder access to the Mana Plane for near-unlimited magical energy constrained only by the user's Magic Circuits. She enables energy projection, creation of A-rank magical barriers, physical protection, regeneration, and strength enhancement, though these prove inferior against Heroic Spirit abilities. She autonomously selects masters and can establish temporary contracts with others if necessary. Her signature functions include "Include" and "Install" operations with Class Cards. She also possesses autonomous flight, wireless video/audio communication with Ruby (vulnerable to magical interference), and hypnosis capable of memory erasure at the cost of the target losing one IQ point—effective even on animals like mice. Like Ruby, she cannot utilize core magical girl abilities without a wielder, and prolonged separation from her user undoes transformations.

Within narratives beyond the core series, such as the "Prisma Causeway" event, Sapphire accompanies Miyu during interdimensional travel when summoned into the Reality Marble of the "First Lady." After Miyu's capture by Connacht ☆ Medb and imprisonment in the Anti-Magical Girl Mystic Code "Voile de Deuil," Sapphire actively searches for her. Upon locating Miyu, Sapphire attempts a rescue but is stopped to prevent energy drain from the restraints. Miyu instructs Sapphire to locate Illya and warn her about the enemy's threat. Sapphire later records and delivers a crucial message from Miyu to Illya and her allies, revealing the First Lady's scheme to trap Magical Girls from multiple worlds. She temporarily contracts with Mash Kyrielight to fend off enemies, facilitating the playback of Miyu's warning. Throughout ensuing battles—including assaults on the First Lady's castle and confrontations with the possessed Chloe von Einzbern—Sapphire provides logistical support, energy transmission, and communication assistance, contributing to the resolution of the Reality Marble incident.