Mystère emerges as an alternate combat persona within Noir, activating during high-stakes confrontations against adversaries such as the Silver Storm. Initially dormant, she designates Noir as her "safe mode," enabling her unrestricted access to Magus Skills beyond Noir’s reach. This duality establishes Mystère as the dominant, battle-ready identity, contrasting Noir’s emotionally restrained and energy-draining baseline state. Her existence originates from an incident where Mystère and Pascale interfaced with Histoire—a repository of pre-apocalyptic technology. This interaction fractured Mystère’s consciousness into Noir’s body, their bond entangled with unresolved questions about Histoire’s true objectives. She holds fragmented memories from two decades before the main events, including Histoire’s hidden location and past clashes involving Drifters like Alba Kuze. These memories fuel her resolve to locate Histoire, cementing her pivotal role in unraveling central conflicts. A critical shift occurs when Mystère cedes her original body to Noir, relocating the latter into Ciel’s vacant Magus frame. This separation grants her autonomous operation while preserving her full abilities. Driven to shield Histoire from hostile forces, she enacts a non-fatal sacrificial act to avert its cataclysmic impact on Earth, simultaneously restoring Magus units corrupted by external tampering. Mystère communicates in third-person with an assertive tone, displaying a tsundere-like sharpness that contrasts Noir’s stoicism. She bluntly critiques Kanata’s Drifter abilities early on, later recognizing his progress. Her narrative role as Noir’s foil underscores themes of integrated identity and responsible technological stewardship. Physically, she possesses dark skin and a ponytail, her hair shifting to black during Magus Skill activation—a visual cue signaling combat readiness. This transformation highlights her link to Noir’s latent potential and their shared roots in Histoire’s systems. Post-separation, she persists as a distinct entity, remaining integral to stabilizing the fractured post-apocalyptic landscape.