Nicolas is a teenage boy originally from Gaul who has spent much of his life enslaved in the Roman mines. Possessing a strong moral compass and protective instincts, he accidentally acquires the magical bulla of Julius Caesar, giving him immense but unpredictable power. He struggles to master his newfound abilities and his own temper while surviving the dangerous political environment of Rome.

General Radulf is a powerful Roman military leader with immense popularity and control over the Praetorian Guard. Originally enslaved after the conquest of Gaul, he rose to prominence as an undefeated gladiator before gaining his military command. He seeks to overthrow the Roman Empire and establish himself as a ruler, aggressively pursuing the magical amulets needed to cement his power.

Aurelia is a pragmatic and resourceful plebeian girl who operates a safe house for vulnerable children in the Roman sewers. Initially wary of Nicolas's volatile magic, she eventually becomes one of his most trusted guides and allies in the city. She harbors personal ambitions and secrets about her past but repeatedly risks her own safety to help those she cares about.

Valerius is a high-ranking Roman senator who outwardly presents himself as a protector of the empire against treason. He provides Nicolas with shelter, fine clothes, and training in magic, though his underlying motives appear driven by his own desire for power. He views the casualties of his political maneuvers as acceptable losses for the greater good of Rome.

Sal is a cruel and vindictive enslaver who oversees the workers in the mines outside Rome. He takes pleasure in tormenting those under his control and harbors a specific disdain for Nicolas. Driven by self-interest and a desire to climb the social ladder, he frequently aligns himself with whoever holds the most influence.

Livia is Nicolas's younger sister, who has spent almost her entire life enslaved in the mines. Having little memory of freedom, she is deeply fearful of punishment and relies heavily on her brother's protection. Despite her difficult circumstances, she possesses a quiet resilience and deeply loves her family.

Caela is a magical griffin whose fate becomes permanently intertwined with Nicolas after he acquires Caesar's bulla. As a creature of myth, she commands immense physical power and possesses a strong psychic bond with the boy who saved her. She becomes both a target for the Roman games and a vital ally in the fight for survival.

Crispus is the patrician son of Senator Valerius. Unlike his politically ambitious father, Crispus shows little interest in the ruthless maneuvers of the Senate. He helps Nicolas adjust to life in Rome, teaching him how to survive the city's social strata and assisting him in practicing his magical abilities.

Felix works for the venatio, preparing animals and enslaved people for the brutal Roman games. While he serves the emperor and often participates in the oppressive systems of Rome, he shows occasional flashes of sympathy toward Nicolas, providing him with critical information about the city's history and the dangers of the bulla.

Horatio is a prominent Roman senator and magistrate who outwardly supports the empire while harboring deep resentments against it. Carrying a heavy grief from his past, he manipulates the Praetorian Guard and sponsors the gladiatorial games to further his own destructive agenda, putting him at direct odds with other Roman leaders.

Tacitus is the reigning emperor of the volatile Roman Empire. Though he rarely appears directly in the daily struggles of the common people, his fear of military uprisings and his orders to acquire the magical bulla drive much of the political conflict in the city.

Halden is the deceased father of Nicolas and Livia. He possessed magical abilities and died tragically in a lightning strike before the events of the story, leaving behind a complex legacy.

Hortensia is the mother of Nicolas and Livia. Originally from a Roman background, she was separated from her children when she was sold by enslavers, leaving Nicolas to care for his younger sister.

Fidelius is an enslaved miner and a friend to Nicolas. He was forced to explore the dangerous cave shafts before Nicolas, an experience that broke his mind and left him completely incoherent.