Levius Cromwell endured profound trauma in the Greenbridge conflict. An automation attack claimed his right arm to corrosive steam, while his mother suffered critical, coma-inducing injuries shielding him. Having already lost his father to the war, Levius was raised by his uncle, Zacks Cromwell.

Physically, he features rose-gold hair, blue eyes, and a cybernetic right arm. He deliberately retains his organic left arm as a tangible link to his mother's sacrifice. His physique stays lean and athletic despite the prosthetics.

His personality blends reserved introspection with fierce determination. Deep loyalty to his comatose mother fuels relentless focus on her recovery and his boxing career. Generally stoic, he exhibits fierce protectiveness when provoked, especially concerning family or past trauma. His persistence drives him into high-risk situations, though he adapts swiftly through observation. Characterization varies: the manga portrays a more ruthless pragmatism, while the anime leans toward comparative idealism.

Levius pursues mechanical martial arts (metal boxing) as career and existential validation. His fighting style incorporates a signature spinning hook technique, consciously avoiding over-reliance. A genetic advantage from Greenbridge's Agartha water grants superior steam manipulation through his cybernetics, manifesting as enhanced punching power despite minimal prosthetic modifications.

Key relationships define his journey: Zacks acts as both parental figure and trainer, providing technical guidance and emotional support. Natalia Garnet serves as a friendly rival, fostering mutual respect through competitive encouragement. A.J. Langdon embodies shared wartime trauma; her conditioning by Dr. Clown compels Levius to free her from exploitation. Dr. Clown emerges as the primary antagonist, targeting Levius for his Greenbridge heritage and steam-manipulation capabilities.

Levius progresses through competitive ranks, initially facing Malcolm Eden. Their manga confrontation ends lethally at Malcolm's request, while the anime adaptation spares him. The battle against Hugo Stratus for Grade I promotion halts when A.J. defeats Hugo first. This reveals Amethyst's involvement via A.J.'s prosthetics, triggering Levius's traumatic memories of Greenbridge's destruction. In their decisive match, Levius disables A.J.'s external steam generator before destroying her internal backup system to break Dr. Clown's control, securing her rescue and his promotion.

His character arc explores trauma processing and identity formation. Retaining his organic arm symbolizes connection to his past, while boxing represents forward momentum. Post-rescue integration of A.J. into his life signifies expanded familial bonds beyond his mother and uncle.