Millaarc Cranstoun began as a failed experiment by the Bavarian Illuminati, engineered through genetic manipulation to replicate mythical vampires. Captured in Slovakia and subjected to torturous procedures, she manifested traits reminiscent of vampiric legends, including mind-invasion through eye contact and a dependency on rare blood. Following the Illuminati’s downfall, she fled with Vanessa Diodati and Elsa Bête, joining Noble Red under Fudou Kazanari’s protection in exchange for aiding his schemes.

Her demeanor veers between a cheerful facade and sadistic glee in battle—a calculated act to spare her allies from morally dark tasks. Despite self-labeling as “weak” compared to figures like Tsubasa Kazanari, she exhibits fierce loyalty to Vanessa and Elsa, often risking her life to shield them. This devotion drives her to undertake brutal missions, from massacring concert audiences to unleashing psychological warfare on enemies.

Millaarc’s powers include bio-enhanced Chiroptera wings for aerial combat and the Stained Glance, a vampiric mind-flaying ability. After Shem-Ha resurrects her, she gains full vampirism: echolocation, bat-inspired evasion, limb regeneration, and independence from external blood. Her combat style evolves with techniques like Two-Platoon Destruction, using duplicates to overpower opponents.

In *Symphogear XV*, she repeatedly clashes with protagonists, targeting Tsubasa with traumatic illusions via the Stained Glance. Though initially defeated, her resurrection transforms her into a deadlier force, eroding her humanity. Her final acts align with Noble Red’s survival-driven vengeance, culminating in a thwarted sabotage of a lunar mission before her space-bound exile.

Her relationships hinge on familial loyalty to Vanessa and Elsa, shouldering roles they refuse. Interactions with manipulators like Fudou and Shem-Ha underscore her role as a pawn in grander plots, while clashes with heroes reflect themes of perceived fragility versus resilience.