Wilbur is a rapidly maturing, unusually large boy living in the isolated village of Dunwich. Though technically a child, his astonishing growth rate means he resembles an adult man by the age of ten. Socially marginalized and emitting a strange odor that aggravates animals, he focuses his time on studying his grandfather's arcane texts. He searches for forbidden knowledge, specifically seeking access to rare texts like The Necronomicon at Miskatonic University.

Dr. Henry Armitage is an academic and the librarian at Miskatonic University in Arkham. Operating far outside the insular culture of Dunwich, he serves as a guardian of dangerous knowledge. When he encounters Wilbur Whateley, he recognizes the danger the young man poses and assumes the heavy responsibility of preventing him from accessing The Necronomicon.

Old Whateley is the patriarch of the ostracized Whateley family and a practitioner of dark magic. Living on the periphery of an already isolated town, he dedicates his life to witchcraft and arcane rituals. He constantly renovates his farmhouse and buys large numbers of cattle, harboring secrets that the rest of the town deliberately ignores.

Yog-Sothoth is an ancient, extra-dimensional cosmic being existing entirely outside human comprehension of time and space. Mentioned frequently in arcane texts like The Necronomicon, this entity serves as the gatekeeper for the Old Ones. It possesses reality-warping power and represents a constant, hovering threat to the fabric of the human world.

The Entity is a mysterious, unseen being harbored inside the Whateley farmhouse. It requires constant space, forcing the family to continually alter their home's structure to contain it. Emitting a foul stench and accompanied by strange noises, the invisible creature strikes deep fear into anyone who passes nearby.

Lavinia Whateley is an isolated resident of Dunwich who experiences severe ostracization from her community. Described as a daydreaming loner, she lives under the heavy influence of her father's obsession with dark magic. She grows increasingly fearful as her son matures at a rapid pace and focuses on the occult.

Francis Morgan is an academic colleague of Dr. Henry Armitage at Miskatonic University. Operating within the relative safety of Arkham, he provides crucial assistance to Armitage when the librarian begins investigating the strange and frightening circumstances surrounding the Whateley family's requests.

Warren Rice is a trusted academic colleague of Dr. Henry Armitage. As one of the few individuals Armitage trusts with his horrifying translations of forbidden texts, Rice steps out of his comfortable university life to confront forces that defy scientific explanation.

Dr. Houghton is the local physician in Dunwich. He represents the rational, scientific perspective in a town steeped in superstition, though he finds himself deeply unsettled by the uncanny noises and strange environmental phenomena at the Whateley farmhouse.

Curtis is a local resident of Dunwich. Like many in the village, he maintains a willful ignorance of the Whateley family's activities until forced to confront the horrifying reality of the supernatural forces gathering in their town.

Earl Sawyer is a resident of Dunwich who participates in the town's delayed response to the mounting danger. He stands with the other men of the village, relying on a telescope to maintain a safe distance from the terrifying events threatening their homes.

Mrs. Frye is a Dunwich local living on a nearby farm with her family. She operates a telephone, serving as a frantic voice of warning when mysterious, large-scale destruction begins to approach her property.