Alex is a young boy who writes scary stories in his "nightbooks" to cope with his bad dreams. He feels isolated and weird compared to other children, driving his initial desire to destroy his work and blend in. Captured by a witch, he relies on his creativity and survival instincts, trading a new terrifying story each night for his life.

Natacha is a young witch who lures children into her enchanted apartment using things they love. She claims to appreciate the dark imagination in Alex's stories and forces him to read to her nightly to soothe the rumbling apartment. She is proud, quick to anger, and demands absolute obedience from her captives.

Aunt Gris is an ancient witch whose immense power fuels the enchanted apartment and its magical creations. She represents the deepest, oldest magic of the dwelling, possessing a terrifying hunger for children and an obsession with frightening stories. Her dark legacy hangs heavily over the apartment's current occupants.

Yasmin is a tough, pragmatic girl who has been trapped in apartment 4E longer than Alex. She tends to the magical plant nursery and prepares meals for the witch. Having witnessed terrible things happen to her previous friends, she maintains an emotional distance to protect herself from further heartbreak.

Lenore is a large orange cat with the ability to turn invisible at will. She acts as a spy in the apartment, watching the captive children and reporting their actions. Despite her initial hostility, she responds to acts of kindness and food offerings.

Claire is a former captive of apartment 4E who used to tend to the magical plants before Yasmin took over the duty. She befriended Yasmin and taught her how to care for the nursery before suffering a tragic fate after trying to sabotage the plumbing.

Eli is one of the previous children lured into the apartment before Alex's arrival. He formed a bond with the other captives during his imprisonment.

Hwan is a former captive who lived in apartment 4E alongside Yasmin, Claire, and Eli. He shared the harrowing experience of captivity with the others.

John is Alex's older brother. Alex views him as a typical "meathead" who is physically strong and brave, contrasting heavily with Alex's own feelings of weakness and cowardice.

Sito is Yasmin's deceased grandmother. Her memory and the traditional Lebanese dishes they used to cook together remain a powerful source of comfort and longing for Yasmin, which the apartment used to trap her.