Norah is a powerful psychic who uses the reality-bending magic of Slade House to extend her life. She appears as a polite, aristocratic hostess to her guests, masking her true nature as a predator who consumes the souls of psychically sensitive individuals. Unlike her brother, she views their endless cycle of feeding with weariness and frustration, feeling increasingly disconnected from her preserved physical body. She meticulously crafts customized illusions to manipulate the specific desires of her victims.

Jonah is Norah's twin brother and a formidable psychic who helps maintain the timeless void known as the lacuna. He takes immense pride in generating the complex physical and temporal illusions that trick their victims into letting their guard down. He possesses an arrogant streak and firmly believes their methods are flawless, frequently dismissing his sister's concerns about potential mistakes. His desire for recognition sometimes leads him to boast about their secret history.

A Black Canadian psychiatrist, Marinus investigates the urban legends surrounding Slade House and the writings of Fred Pink. She belongs to Horology, a faction of immortals who dedicate themselves to protecting ordinary humans from predatory psychics. Highly perceptive and magically gifted, she enters the Grayers' domain with a clear understanding of the danger and a strategy to dismantle their operation. She views the preservation of human life as a sacred duty.

Sal is a university student who joins a paranormal investigation group primarily to spend time with her crush. She struggles with intense insecurity and low self-esteem, stemming from childhood bullying and the shadow of her highly successful older sister. Her latent psychic potential makes her a prime target for Slade House, where her deepest desires and fears are weaponized against her.

Gordon is a gruff, divorced police detective facing an internal inquiry and mounting financial debt. He visits Slade Alley to investigate the disappearance of the Bishop family, a task he initially treats as an annoyance. Desperate for validation and human connection, he easily falls prey to the flattering illusions presented to him by the Grayers. He tries to view himself as a noble protector despite his history of domestic abuse and professional misconduct.

Rita is a divorced musician and single mother struggling to manage severe financial debt. She receives an invitation to a soirée at Slade House and brings her son along, hoping to secure employment from wealthy Arts Council members. Her desperation for financial security blinds her to the strange inconsistencies of the house and its hosts.

Nathan is a thirteen-year-old boy coping with the trauma of a vicious dog attack and ongoing bullying at school. He attends the Slade House soirée reluctantly, finding the hidden garden entrance through his innate psychic sensitivity. In the garden, he bonds quickly with a boy his age, unaware of the trap closing around him.

Freya is a successful journalist working for Spyglass Magazine in London. She carries immense guilt for neglecting her younger sister prior to her disappearance, driving her to aggressively pursue any available clues. Her pragmatic and skeptical nature makes her highly resistant to the supernatural stories presented to her, demanding concrete proof at every turn.

Fred is a former window cleaner who dedicates his life to uncovering the truth about Slade House. He suffers a severe accident in the alley but eventually wakes to share his findings with anyone willing to listen. His obsessive pursuit of the Grayer twins leads many to dismiss him as unstable, yet his extensive research proves vital to those investigating the disappearances.

Todd is a university student who serves as the vice president of the campus paranormal club. He chose a local university to remain close to his elderly father and blind mother, demonstrating a strong sense of familial duty. His kind and attentive demeanor makes him the object of Sal's quiet affections.

Axel is a postgraduate university student who leads a campus group dedicated to investigating the supernatural. He organizes the excursion to Westwood Road based on the persistent claims of his uncle. When the group seemingly finds a normal student party instead of a haunted house, he quickly retreats in embarrassment.

Fern is a university student who joins the Paranormal Society as a way to process her grief. Following the tragic death of her brother, she seeks out supernatural phenomena in hopes of finding proof that human consciousness survives physical death.

Léon is an early twentieth-century doctor with a deep interest in the occult and spiritualism. He recognizes the immense value of the Grayer twins' telepathy and transports them to North Africa for formal training. He later manages their lucrative careers as spiritualists in America, though his desire to publish their secrets ultimately causes friction.

Frank is a military trainer living in Zimbabwe and the ex-husband of Rita Bishop. He appears primarily within a vividly constructed illusion tailored to manipulate his son's sense of safety and reality. He projects an image of casual domestic authority.

Joy is Frank Bishop's partner in Zimbabwe. She appears in a domestic setting, silently serving coffee and food while conforming to Frank's instructions.

Lance is an abrasive member of the university's Paranormal Society. He lacks social grace and frequently makes others uncomfortable, later appearing as a grotesque figure within Sal's drug-induced hallucinations.

Angelica is a university student who participates in the Paranormal Society. She frequently debates with other members about psychic potential and actively searches for supernatural anomalies during their field trips.

Avril is Freya's romantic partner living in London. She acts as a grounded support system, offering to fake an emergency call to help Freya escape an uncomfortable interview situation.

Jonny is Fern's deceased brother. His tragic death profoundly affects his sister, driving her to seek out evidence of ghosts to ensure his spirit still exists.

The Sayyid is a mystical figure belonging to the Shaded Way. He takes in the young Grayer twins to hone their psychic abilities, eventually declaring that he has exhausted his knowledge in training them.

Gabriel is a late nineteenth-century gamekeeper at Swaffham Manor and the father of the psychically gifted twins. He dies in a tragic shooting accident when his children are very young.

Nellie is the mother of the Grayer twins. Following the sudden death of her husband, she relies on the charity of her wealthy employers to keep her family on the estate.

Albertina is a wealthy aristocratic woman who oversees the estate where the Grayer twins are born. Following the tragic loss of her sons in World War I, she turns to spiritualism and cocaine elixirs to manage her overwhelming grief, allowing a foreign medic to manipulate her household.