Lale is a multilingual young Slovakian Jew imprisoned at Auschwitz-Birkenau. Forced into the role of the camp's Tätowierer, he must permanently mark his fellow prisoners with identification numbers. He utilizes his natural charm and the slight privileges of his position to organize a black-market trade system for food and medicine. He relies on his deep moral code and devotion to others to survive the daily horrors of the camp.

Gita is a young Slovakian woman who works in the administration building at Auschwitz, transcribing prisoner records. She initially hides her last name from Lale out of a deep-seated fear and a desire to detach from her past. Despite the traumatic conditions that threaten to break her spirit, she maintains fierce loyalty to her close circle of female friends.

Baretski is a young Romanian SS officer assigned to be Lale's minder. He possesses a highly volatile temper and treats the prisoners with sadistic cruelty. Despite his position of power, he exhibits a childish insecurity and occasionally treats Lale as a confidant regarding his romantic life.

Schwarzhuber is a high-ranking commander at Auschwitz. He is described as a man whose soul has completely died. He uses his position of absolute authority to systematically abuse female prisoners, viewing them entirely as property for his own gratification.

Josef Mengele is a terrifying SS physician stationed at Auschwitz. He searches the incoming transports for specific types of prisoners to use in his horrific medical experiments. He inspires dread in both the prisoners and the other SS guards through his unpredictable and clinical cruelty.

Houstek is an SS commanding officer overseeing the operations at Auschwitz. He formalizes Lale's position as the primary tattooist. He manages the camp with strict efficiency and oversees the punishment blocks where rule-breakers are sent.

Rudolf Hoess is the Commandant of Auschwitz. He officially welcomes the prisoners with threats of extreme consequences for disobedience. He represents the highest level of the Nazi apparatus operating within the camp.

Jakub is an American Jew of Polish descent who becomes trapped in Europe and sent to Auschwitz. Because of his immense physical size and strength, the SS assign him to brutal physical labor. He must carefully balance the horrific demands placed on him by the Nazi guards with his desire to retain his humanity.

Cilka is a strikingly beautiful Jewish prisoner assigned to administrative duties. Unlike other female prisoners, the guards allow her to keep her long hair. This physical distinction draws the unwanted attention of high-ranking SS officers, placing her in an extremely dangerous and isolating position.

Victor is a Polish civilian construction worker employed by the Germans to build infrastructure at Birkenau. He recognizes the starvation suffered by the prisoners and chooses to risk his own life to provide them with sustenance. He establishes an illicit trade network with Lale, exchanging food and medicine for smuggled valuables.

Yuri is a Polish civilian laborer who accompanies Victor into the concentration camp. He is initially much more hesitant than Victor about interacting with the prisoners and fears the wrath of the SS. He eventually warms up to Lale and actively participates in their high-stakes smuggling operation.

Pepan is a French economics professor who occupies the position of Tätowierer at Auschwitz. Imprisoned for his radical political beliefs rather than his religion, he enjoys slight privileges. He acts as a mentor to Lale, teaching him that taking on a morally compromising job is sometimes necessary to survive.

Aron is a young Jewish man who immediately gravitates toward Lale's quiet authority on the transport train. He relies on Lale's advice to avoid fighting back against the armed guards. He demonstrates immense courage by risking his own safety to protect Lale when sickness strikes the camp.

Goldie is Lale's younger sister. She remains a constant source of motivation for Lale during his darkest moments in the camp. Before the war, she lived a comfortable life with her family in Krompachy.

Leon is a young prisoner thrust into the position of assistant tattooist. He lacks the political protection and interpersonal skills that keep Lale relatively safe, making him a frequent target for Baretski's physical violence. He works long hours alongside Lale, marking the seemingly endless lines of prisoners.

Dana is a young female prisoner who forms a tight-knit support system with Gita and Ivana. She helps organize the smuggling of valuables from the warehouse where confiscated belongings are stored. She is fiercely protective of Gita when illness sweeps through their block.

Ivana is part of Gita's close circle of friends. She relies on their mutual bond to endure the psychological and physical punishments inflicted by the SS. She works actively to keep her friends safe from the guards' scrutiny.

Nadya is a Romany woman who loses her husband to typhus shortly after arriving at Birkenau. She forms a surrogate family bond with Lale, who is assigned to share a block with the newly imprisoned Romany people. She reminds Lale of his own mother.

Max is Lale's older brother who has a wife and children. He initially volunteers to fulfill the government's demand for Jewish labor, but Lale insists on taking his place to keep the family intact.

Mrs. Goldstein is an older Jewish woman from Vranov and Topl'ou, Gita's hometown. Her arrival in the camp brings devastating news about the fate of the remaining Jewish families in Slovakia.