Leonardo da Vinci manifests as a Caster-class Servant contracted to Chaldea Security Organization. Historically recorded as a peerless male Renaissance genius, this incarnation appears female, having chosen the form of the Mona Lisa to embody the ideal beauty pursued during life, reflecting cultural evolution toward feminine aesthetics. This manifestation stems from self-awareness as the "Universal Man" (Uomo Universale), transcending gender through omnipotent capability. Summoned as Chaldea's third Heroic Spirit during FATE system instability, initial transient existence was circumvented by constructing a duplicate puppet body, enabling permanence through self-assertion as Master. This technique mirrors methodologies of an unnamed doll maker. She retained residence due to fascination with Chaldea's mission and persuasion by Romani Archaman, serving as technical adviser supporting Rayshifts with multidisciplinary expertise. Her personality balances rational assessment of capabilities with childlike curiosity, maintaining composure where others might falter. As a self-aware omnipotent genius, unexpected situations provoke keen interest rather than distress. Eccentricities include nude wandering post-bathing regardless of company and a penchant for eavesdropping, particularly on Romani. A mechanical bird companion reflects her affection for avians, influencing designs like the Ornithricopter desert vehicle. She considers the Master a "pupil," adopting an approachable teacher role over authoritative mentorship. Relationships include collegial friendship with Romani Archaman, acquaintance with idealist magus Makiri Zolgen, and rivalry-turned-mutual respect with Michelangelo—recognized as an equal in fine arts despite historical friction. Sherlock Holmes provokes irritation through comparable genius. Side narratives reference modeling for Verrocchio's Tobias and the Angel, unresolved guilt over mother Caterina's death during the Virgin of the Rocks commission, and conflicted reunion with assistant Salaì's spirit. Capabilities include Territory Creation (10% Arts enhancement) and Item Construction (10% debuff success rate) as class skills. Active skills encompass: Natural Born Genius (self-defense/NP damage boost, Guts status); upgraded Golden Rule (Body) providing debuff immunity, HP/NP regeneration, and party Arts enhancement; and Independent Action enabling NP charge, Invincibility Pierce, and critical stars. The Noble Phantasm Uomo Universale deals AoE Arts damage with NP strength reduction and skill seal effects. A Bond Level 15 passive increases party Bond Points by 25%. During Solomon's Time Temple incursion, she provided technical oversight supporting Master Ritsuka Fujimaru and Mash Kyrielight. She identified Beast-class energy permeating the space and revealed Romani Archaman's decade-long preparations against humanity's incineration, foreseen through Solomon's clairvoyance. She survived Lev Lainur's assassination attempt due to Ritsuka's intervention. Post-conflict, a younger variant ("Da Vinci Lily") appears, modeled after the unfinished equine sculpture Gran Cavallo and commanding the Shadow Border vehicle resembling armored tank designs.