Deeti is a young, high-caste Rajput woman who farms poppies to support her family. Her most distinctive physical feature is her light grey eyes, which give her a penetrating gaze. Burdened by her husband's severe opium addiction and the resulting poverty, she relies on her strong maternal instincts to protect her young daughter. When circumstances force her from her home, she demonstrates remarkable adaptability.

Kalua is a low-caste ox-cart driver known throughout the region for his massive size and dark skin. People often mistake his quiet demeanor for a lack of intelligence, regularly taking advantage of him in cruel ways. Beneath his silent exterior lies a sharp mind and a capacity for swift, decisive action when protecting those he cares about.

Bhyro Singh is a former soldier in the East India Company's army and the uncle of Hukam Singh. He is a bull-like, imposing man who expects complete obedience from his family and subordinates. As a subedar on the Ibis, he abuses his authority to enforce rigid hierarchies and exact brutal punishments on anyone who crosses him.

Zachary is an American sailor from Baltimore, born to a freedwoman but capable of passing as white in the rigidly stratified society of the British Empire. Originally a shipyard worker, he finds himself rapidly promoted on the Ibis out of sheer necessity. He tries to adopt the manners of a gentleman to survive in Calcutta, balancing his innate moral compass against the demands of his wealthy employers.

Serang Ali is the enigmatic leader of the lascar crew aboard the Ibis. His origins are entirely unknown to the rest of the crew, and he speaks in a heavy sailor's pidgin. He acts as a shadow captain, expertly handling the ship while pushing Zachary to assume the public role of authority.

Benjamin Burnham is a powerful British merchant and shipowner who built his massive fortune in the opium trade. Despite his wealth, he is a self-made man who survived a brutal childhood as an indentured servant. He firmly believes that free trade and British imperialism are divine rights, using his extreme religious views to justify aggressive business tactics and the exploitation of others.

Paulette is the orphaned daughter of a French botanist. Having been raised primarily by a Bengali wet nurse, she feels entirely out of place in the rigid, polite European society of the Burnhams' household. She prefers wearing saris and speaking Bengali, finding the restrictions placed upon European women suffocating as she searches for a way to escape to Mauritius.

Jodu is a young Muslim boatman from Naskarpara who grew up alongside Paulette Lambert. After his boat is destroyed by the Ibis, he takes the opportunity to fulfill his dream of becoming a deep-water lascar. Although initially mocked by the ocean-going sailors for his freshwater background, his agility and determination quickly earn him respect.

Neel Halder is the Raja of Raskhali, an aristocratic zemindar whose family fortune has been heavily depleted by his father's extravagant spending. Bookish and accustomed to a life of extreme privilege, he finds himself completely unequipped for the harsh realities of the British legal system when his debts catch up to him. Stripped of his wealth and caste, he must learn to survive in entirely new circumstances.

Mr. Crowle is the brutal first mate of the Ibis. A massive, hunched man who constantly seeks to establish dominance, he takes immense pleasure in terrifying the crew and the indentured migrants. He views any insubordination as a personal attack and actively targets those who show vulnerability or difference.

Nob Kissin serves as the gomusta, or primary agent, for Benjamin Burnham's trading empire. Originally trained as a holy man, he abandoned his temple duties out of devotion to a woman named Taramony. Following her death, he becomes increasingly focused on spiritual signs, undergoing a gradual physical and emotional transformation as he searches for her reincarnated presence.

Chillingworth is the aging, world-weary captain of the Ibis. Preparing for his final voyage, he projects an aura of absolute authority and strict adherence to maritime law. However, his stern public persona masks a deep cynicism regarding the British Empire's motivations and a private dependency on opium to cope with the isolation of life at sea.

Ah Fatt, whose birth name is Lei Leong Fatt, is a Chinese prisoner from Canton slated for transport to Mauritius. The son of a wealthy father and a washerwoman, he grew up torn between different cultural expectations before falling into deep addiction. In prison, he forms an unlikely but profound bond with his cellmate.

Hukam Singh is Deeti's husband, a high-caste Rajput who works at the Sudder Opium Factory. He is a quiet, drowsy man whose life has been entirely consumed by his severe addiction to opium, rendering him incapable of fulfilling his marital or familial duties.

Kabutri is Deeti's young daughter. She is innocent and curious about the world outside their village, completely unaware of the dark circumstances surrounding her conception or the imminent collapse of her family's stability.

Munia is a young, lively indentured migrant woman heading to Mauritius. She is eager for new experiences and quickly becomes fascinated by the sailors on the ship, particularly Jodu. Her youthful indiscretions frequently draw the harsh attention of the ship's guards.

Justice Kendalbushe is an older, devoutly Christian judge who moves in the same high-society circles as the Burnhams. He views himself as a paragon of civilized British justice, using his courtroom to lecture locals on morality while simultaneously using his status to pursue inappropriate romantic interests.

James Doughty is a boisterous, heavily drinking river pilot who guides ships through the treacherous local waters. He speaks in a dense slang that mixes English with local dialects and holds deeply entrenched prejudices against the native population, despite regularly partaking in their services.

Mrs. Burnham is the strict, socially ambitious wife of Benjamin Burnham. She rigidly enforces European etiquette within her household and views Paulette's Bengali upbringing as a flaw that must be corrected through scripture and a respectable marriage.

Malati is Neel Halder's wife. Despite the strict caste rules that governed their aristocratic life, she demonstrates surprising resilience and loyalty when Neel is stripped of his title and wealth, willing to cast aside tradition to support him.