Cia is a 16-year-old recent graduate from the rural Five Lakes colony who dreams of advancing to the University. She possesses strong mechanical and problem-solving skills fostered by her family's agricultural background. Resourceful and naturally trusting, she soon faces her father's troubling warnings about the true nature of the government's selection process as she travels to Tosu City.

Tomas is a handsome, intelligent young man from the Five Lakes colony chosen alongside Cia for The Testing. He is charming and confident, quickly forming a close partnership with Cia as they endure the preliminary stages of their journey. He proves highly protective and instinctively wary of the other candidates surrounding them.

Will is a Testing candidate from another colony who quickly befriends the Five Lakes group alongside his brother, Gill. He appears friendly and relieved to find peers who share his anxieties about the grueling exams. As the trials progress, he demonstrates a fierce drive to succeed and survive the extreme conditions.

Dr. Barnes is a high-ranking official overseeing The Testing in Tosu City. He maintains a cold, utilitarian philosophy regarding the candidates, viewing the intense pressure and resulting casualties as a necessary filter to identify the United Commonwealth's future leaders.

Cia's father is a respected agricultural innovator in the Five Lakes colony who previously attended the University. He works on genetically altering plants to survive in blighted soil. Despite his prestigious past, he is haunted by dark, fragmented nightmares of his own Testing experience, prompting him to secretly warn his daughter about the dangers ahead.

Zeen is Cia's older brother and a talented agricultural worker in the Five Lakes colony. He recently developed a new strain of potato, though his father publicly took credit for the invention to keep Zeen off the Testing officials' radar. Zeen harbors a deep desire to leave the colony and see the broader world.

Michal is an official from Tosu City tasked with escorting the chosen candidates from the Five Lakes colony. He explains the strict rules of the process and the severe penalties for treason. During the journey, he offers Cia subtle warnings and advice, indicating he holds a specific interest in her potential.

Malachi is a shy, sweet-natured student from the Five Lakes colony. He is chosen alongside Cia, Tomas, and Zandri to travel to Tosu City. Placed in the triangle testing group, he struggles with the immediate hostility of the other candidates and the intense pressure of the exams.

Zandri is a beautiful, artistic graduate from the Five Lakes colony. She is openly rebellious, immediately questioning what happens if a candidate refuses to participate in The Testing. Assigned to the square testing group, she relies on her creativity as she faces the strict Tosu City administration.

Ryme is a Testing candidate from another colony who becomes Cia's roommate. She initially offers Cia food, but soon displays a highly competitive and paranoid demeanor. She treats the exams as a high-stakes competition and reacts poorly to the extreme stress of the academic environment.

Gill is a Testing candidate who bonds with the Five Lakes students over the extreme difficulty of the written examinations. He experiences the early stages of the competition alongside his brother Will, seeking safety and reassurance in numbers.

Roman is a confident and highly competitive Testing candidate assigned to work with Cia during the team examinations. He quickly asserts himself by taking the lead on the first question, demonstrating a self-serving strategy designed to put his peers at a direct disadvantage.

Daileen is Cia's closest friend in the Five Lakes colony. The two share a deep bond, forged years earlier when Cia intervened during a dark period in Daileen's life. Daileen is visibly devastated by Cia's selection for The Testing, knowing her friend will likely never return to the colony.

Stacia is a pragmatic Testing candidate who encounters Cia and Tomas in the wilderness. She holds strong opinions about the nature of the United Commonwealth, believing that a willingness to use deadly force and display a "killer instinct" are necessary traits for successful leaders.

Vic is a Testing candidate navigating the wilderness portion of the exam. He travels in a small group and openly questions why other competitors, like Cia, would choose to share their resources rather than hoard them for personal gain.

Tracelyn is a Testing candidate traversing the desolate terrain. Unlike her companion Stacia, she expresses confusion and horror at the idea that candidates would actively attack or kill one another to succeed in the Commonwealth's trials.

Brick is a Testing candidate placed in Cia's group for the teamwork stage. He is determined to answer his assigned question to secure a passing grade, forcing Cia to intervene and warn him about the potential sabotage hidden within the test's structure.