Kelvinius was the featured Warrior Beast on Episode 16 of the Great Mazinger series and one of a few Warrior Beast to show a background story prior to his conversion, the other been Jerunicas. Kelvinius was the former young and brash Prince of the original Mikene Empire prior to the take over and was captured along with his former lover when the Great General and his Soldiers shutdown them down with arrows. After the population was enslaved, the Prince's brain was incorporated into a SuperHuman Warrior Beast that resembles a large winged humanoid with light red skin, yellow wings, a purple tunic with black bands, a belt buckle that resembles a demonic face, had a feathery collar, a hat with a blade on top and wings on the side, and a pair of sandal-like boots with small wings near the back. He wielded a trident that could ignite and burn any enemy on contact, and carried a small circular shield on the right hand. Despite having the two face design seen with many Warrior Beasts, his brain was located on the actual head of the Cyborg.

Kelvinius due to his heritage as the prince of Mikene demands respect from his peers, even from his supposed superiors as his brain didn't seem to have been fully conditioned in the same way other Warrior Beasts do and is reminded he carries a bomb in case he goes out of line. As such he usually just lies around, constantly dreaming of the Happier Times and hoping for their return, ending with the nightmare of the day of the take over, which would leave him in a state of anxiety and screaming while been carried away. General Julicaesar viewed him as rebellious and incapable of submitting to orders. When he is finally commission to take on Great Mazinger, The Great General express that he didn't care if he fell in battle, but would take the glory of victory if he succeeded either way.

Despite refusing at first, Kelvinius finally willingly deploys into action when Julicaesar (lying of course) promises him the Throne of Mikene if he fought and destroy the Great Mazinger. He first encounter and fought Boss Borot at Boss' annoying insistence, then he met and reluctantly fought Venus A, beating the two and forcing Jun and Boss to call in Tetsuya and Great Mazinger – which finally force Great Mazinger out, giving Kelvinius the match for the throne he wanted.

In the fight, both warriors cut off their wings - Tetsuya express openly to him be more than a Beast, which Kelvinius' confesses who he was and motives to fight. His Spear and Shield are later melted by Great's Breast Burn, leaving him defenseless, but before Great Mazinger could destroy Kelvinius, Jun intervenes for him and begs Tetsuya to let him explain as Kelvinius kneels in disgrace to his turn of fortune. Julicaesar tries to talk him to commit suicide by blowing up with Great with the bomb he carries, which at first he attempts to, but this forces an outburst of emotion from the Prince, recognizing that even if he won, there was no guarantee freedom for his people as they are all now Mikene Soldiers or just brains inside Warrior Beasts and request Great to kill him. Tetsuya made Kelvinius realized that he was fighting the wrong enemy all along, and that if he wanted the throne back he should fight the Great General – Julicaesar, seeing the turn of events, orders a Mikenes Trooper to destroy the prince.

In his damaged and exhausted state, and seeing the Mikelos rushing towards them, Kelvinius bids farewell and launches himself into the Warship, blowing up inside. This finally forces Julicaesar to retreat. All that remained of the Prince was a falling piece of his wings, as Tetsuya, Jun and Boss mourned his death.

The Fate of Kelvinius lover is unknown ... although my bet falls on a certain Marquis.

Kelvinius only other cameo in the franchise is in the opening sequence of Mazinkaiser vs the Great General of Darkness Deathmatch - jumping from the Mikelos to attack a city.