Radium Lavans serves as a lieutenant in the Martian liberation group BAHRAM. Initially a LEV pilot, he exhibits a reckless combat style and harbors profound hatred for Earth-born humans (Earthers). This animosity arises from systemic oppression against Martians, physically weaker due to Mars' lower gravity, and intensifies after witnessing a UNSF soldier assault his comrade William without repercussions. His volatile nature surfaces in training simulations where he employs suicidal tactics.

Recruited as a test pilot for the prototype Orbital Frame Idolo, Radium develops an exclusive symbiotic bond with the machine following metatron exposure during testing. This bond physically fuses him with the Frame, preventing others, like comrade Viola Gyune, from piloting it. Prolonged exposure to Idolo's metatron systems triggers progressive psychological deterioration, manifesting as arrogance, combat sadism, and eventual psychosis. He experiences delusions of grandeur, believing himself immortal alongside Idolo, and displays violent outbursts, including nearly beating an Earther spy to death.

Radium's mental state collapses completely when his fiancée, Dolores Hayes, is killed during a UNSF hostage rescue on Deimos Station. Idolo responds to his grief by generating a hallucination of Dolores, pacifying Radium while operating autonomously. Within this delusion, he marries Dolores in a chapel, rejecting Viola's attempts to wake him. Simultaneously, the damaged Idolo battles combined UNSF and BAHRAM forces until its destruction. Radium is presumed dead.

He survives the Deimos Incident through BAHRAM intervention, resurrected as a cyborg with metatron-based cybernetics. Adopting the alias Napth Pleminger as cover, he inherits a fortune and covertly leads BAHRAM. He adopts orphaned siblings Rebecca, Axel, and Rully Hunter, indoctrinating them into anti-Earth ideology. His vendetta intensifies upon learning an Orbital Frame named Isis identifies as "Dolores," which he perceives as an insult to his late lover's memory. Piloting the Orbital Frame Hathor, he launches a genocidal campaign to destroy Earth's Orbital Elevator.

During the final assault on the elevator, Radium confronts the Dolores Orbital Frame and its pilot James Links. Hathor generates another chapel hallucination, where Radium battles a manifestation of James while denouncing Viola (linked to Rebecca) and all others as "trash" unworthy beside Dolores. Briefly recognizing Dolores' essence within the Frame's AI, he nevertheless refuses redemption. After a protracted battle, Dolores and James cripple Hathor. In his dying moments, Radium experiences a vision of Dolores' daughter and merges Hathor, his Raptor drones, and residual metatron energy to stabilize the collapsing elevator, sacrificing himself with a final smile.

A persistent inconsistency exists regarding his name, with variations like "Radam" appearing in related media, though the anime exclusively uses "Radium."