Life had been rough for the boy since the beginning, having grown up in the Manhattan Italian slums and first his father and then his mother at the age of 9. The young Italian/American boy stuck it out as best he could, times being dangerous and unmerciful in the early years of the Roaring Twenties. Firo Prochainezo was found and taken in by the Martillo Family, a branch of the Camorra. The years of the Prohibition Era were soon upon them, but the underground activities of mafia violence only surfaced in a much corrupted New York. As a young adult not yet crossed into his second decade of years, Firo was promoted within the Camorra, in particular becoming a representative of the Martillo Family under the watchful eye of Maiza Avaro.
It was around this time that many things were happening and soon converged upon each other. A long time rival of Maiza's made his appearance, buried secrets suddenly exposed. More than hundreds of years older than any normal human being, Maiza Avaro and Szilard Quates were revealed to be immortals, gifted with the elixir of life by a demon they had summoned into being centuries back, a group of ambitious alchemists aboard a galleon headed for the new world. Szilard had been working all this time to recreate the liquour of immortality, and had finally succeeded. Unfortunately, the majority of the finished products were destroyed in a fire, and the two bottles that had been preserved escaped from Quates' grasp, changing hands between many a mafia lord before finding its way into the serving glasses of the Camorras and their close associates.
Szilard arrived too late to recover the elixir, but he was not so put off as to attempt to absorb Maiza, as the only way to destroy the immortals was for another immortal to 'eat' them, absorbing their being into themselves. During Szilard's face off with Maiza, Firo was given a crash course in the existence of immortals by Szilard's homunculus, Ennis. Perhaps due to the unspoken feelings he had developed for the girl, as well as Ennis's desire to be something more than just a servant, that boundaries of trust were overcome and she betrayed her master, telling Firo how to annihilate Szilard. This was only after finding out that the Camorras had partaken of the immortal elixir accidentally, a fact that Szilard had missed after he had thought to have gunned most of them down. In a last desperate attempt to ensure his survival, Szilard Quates made a lunge for Firo to try taking down the sudden new threat. His effort was nullified by the boy's sharp knife, and before the man could properly regenerate, Firo's hand settled upon the old man's head with the unvoiced command, 'Eat.'
With Szilard defeated, the Camorras rejoiced at their newfound immortality, and Firo freed Ennis of the power he gained from Szilard in being able to control her as a homunculus. The shy but fond looks he gave the girl were not unnoticed by Maiza, whom after briefly distressing about the newly spread curse of immortality, silently decided that perhaps this would be all right…
For a member of the Camorra, Firo's a surprisingly friendly sort. Considerably bold, he isn't afraid to confront people, nor is he worried about the impression he leaves since he's simply being himself. He's a representative of the Martillo Family, and coming from the city and age of mafias and power struggles, it's a fact that he flashes as readily as a police badge. If anyone knows anything of the Camorras, then they know well not to give the boy trouble, or they'll find out just how much trouble they've gotten themselves into. And for those stubborn and upset enough, they'll know which clan to direct their ire towards if they're made a fool of.
It's not to say that Firo actively looks for trouble himself… but things happen, and as a young man having chosen a dangerous path in life, he's not about to let such details get in the way of him experiencing new things. This goes hand-in-hand with his tendancy to meddle, but he means well, really. Sometimes he just can't help himself; if something's going on and he just happens to be around, more often than not, Firo will go to investigate, or jump into something that didn't originally involve him. He's not afraid of the consequences. It isn't only due to his immortality. There's little one needs to fear when even death holds no claim on them. But even before gaining such a trait, Firo was never afraid to take risks, to live life on the edge. There was no hesitation in his decision to join the ranks of the Camorra, and he's never been one to back out on anything once setting his foot in.
He has street smarts, but he also has something else- the knowledge of many an immortal before him. After absorbing the immortal known as Szilard Quates, Firo has gained not only the knowledge and experience of the old alchemist, but of all of Quates' victims before him. Among what has been passed on to Firo, likely the secret of creating the elixir of immortality as Quates had gained when he 'ate' Maiza's younger brother long ago after having found out that Maiza had passed along that knowledge to him. With this newfound knowledge, Firo also learned how he could break the control Quates had on Ennis to allow the Homunculus a chance to live life as any other person would, and although his feelings for her are rather obvious at times, he still has a tendency to be shy in expressing them to her.
Immortality! He is one of the Camorra that accidentally came to find themselves immortal after consuming a specially concocted elixir. The process of aging is ceased. Injuries, no matter how great or small, quickly mend as if nothing had happened. Limbs and body parts sliced away, blood that pours and drips, it all returns back to the Immortal whom it belongs to. It seems that no matter how severe the damage done, how mutilated a body may be, an Immortal becomes fully restored, even from their supposed death. The only way to 'kill' an Immortal of their type is by absorption at the hand of another Immortal (pun fully intended!). This is done by placing their right hand on another immortal's head and giving the mental command to 'eat.' The body and soul of the Immortal is then absorbed into that hand to become one with the other immortal, and thusly the immortal gains the memories/experiences of the victim. In a similar manner, information can be shared between other Immortals and homunculi, at least of the same origin as their world. If an Immortal wishes to impart knowledge to a fellow Immortal, then they simply set their right hand upon the other's head and mentally will what they wish to pass on to the other.
Unnatural abilities aside, the kid's not at all bad in hand-to-hand fighting, toughing it out on the streets of New York at a young age and having his skills honed by knowledgable members of the Camorra once he was taken under their wing. He's familiar with martial arts and certainly knows how to wield a knife.