Medardo is a young, inexperienced nobleman who suffers a catastrophic cannonball wound during his first battle. The injury obliterates his left side, but military doctors manage to preserve his living right half. He returns to his ancestral home a literal half-man concealed beneath a black cloak. His physical division initiates a reign of terror, as he violently imposes his cruel whims upon the estate.

The unnamed narrator is Medardo's young nephew who lives a relatively unsupervised life within the Terralba castle. Existing on the margins of the noble family, he freely roams the countryside and interacts with various social classes. His childhood innocence provides a neutral lens through which the community's horrific and bizarre events are processed.

Pamela is a pragmatic and grounded young goatherd who lives close to the natural world. She becomes the unfortunate target of Medardo's affections, receiving grotesque tokens of his love in the form of mutilated animals. Recognizing the danger of his obsessive attention, she demonstrates strong survival instincts by fleeing to a forest cave.

Dr. Trelawney is an English physician and former naval doctor stranded in Terralba. He actively avoids practicing medicine, finding the reality of human illness and blood terrifying. Instead, he distracts himself with harmless scientific hobbies and natural observations, deliberately ignoring the suffering caused by Medardo's regime.

Sebastiana is the long-serving family nurse who has raised generations of the Terralba nobility. She acts as the primary stabilizing force in the household, relying on traditional herbal knowledge and strict maternal authority. Her loyalty is severely tested when she becomes a target of Medardo's destructive purges.

Pietrochiodo is the resident master carpenter at the Terralba estate. He possesses immense mechanical talent but finds himself forced into becoming an instrument of state terror. He suffers deep psychological distress as his beautiful craftsmanship is continuously utilized for torture and death.

Ezekiel is the harsh, demanding patriarch of an exiled Huguenot farming family living on Col Gerbido. Having survived religious persecution, he imposes a life of punishing agricultural labor and theological rigidity on his household. He views every hardship as a test of faith and constantly anticipates divine punishment in the form of famine and plague.

Esau is the young son of the Huguenot leader Ezekiel, living under strict religious rule at Col Gerbido. He reacts to his father's crushing moral expectations by actively pursuing minor sins, theft, vandalism, and mischief. His cheerful criminality serves as a direct rebellion against his family's oppressive piety.

Viscount Aiolfo is Medardo's elderly father, a man who has surrendered all his feudal responsibilities to live exclusively among his birds. Unable to cope with the changing world, he seeks solace in natural harmony. His fragile constitution fails him completely when confronted with the horrific reality of his son's physical and moral condition.

Kurt is a pragmatic military squire tasked with accompanying the Terralba heir to the Christian army's camp. He possesses a grim understanding of warfare and its ecological consequences, attempting to educate his inexperienced lord on the brutal realities of the battlefield.

Galateo is an affable resident of Pratofungo, the isolated village for people afflicted with Hansen's disease. He functions as the primary point of contact between the marginalized colony and the surrounding healthy population, utilizing a special horn to announce his approach during his alms-collecting rounds.

The Emperor is the supreme commander of the Christian forces fighting in Bohemia. He views his soldiers and officers as mere mechanical pieces in his strategic games, promoting inexperienced men to high ranks with casual indifference.