Peter is a timid 16-year-old orphan with a pale face and whitish-blond hair. He frequently retreats into trances about happier times to escape the harsh reality of his current situation. Initially fearful, he often relies on others for guidance and feels overwhelmed by the bizarre, ceilingless environment.

Lola is a brash, practical 16-year-old orphan with dark eyes and olive skin. She has a history of getting into trouble with authority figures at her state home. Quick to assess their dire situation, she naturally tries to take charge and establish order, though her aggressive demeanor sometimes alienates the others.

Blossom is an orphan who recently lost her parents, making her the only one in the group who remembers life outside state-run megastructures. She is overweight and wears a frilly dress, reflecting her upper-class background. She acts haughty and is quick to exploit the insecurities of those around her.

Abigail is a tall, slender 16-year-old orphan with pale hair and a serene face. She is a quintessential people-pleaser who has been deeply conditioned to follow rules and maintain social etiquette. Her lack of independence makes her passive, and she worries heavily about what others think of her.

Oliver is a handsome, confident, and athletic 16-year-old orphan. He quickly attempts to assert dominance and control over the group, thriving on the admiration and submission of others. Despite his outward bravado, his need to be in charge masks a deeper insecurity about his influence over people who do not readily submit to him.

Jasper is Peter's former best friend from the state home where they previously lived. Although he is not physically present in the staircase environment, he looms large in Peter's mind as a symbol of safety and familiarity.