The Biologist is a scientist specializing in transitional environments and serves as the narrator of the 12th expedition. She is highly independent and prefers the silent observation of ecosystems over human interaction. During an early exploration of an underground structure, she inhales mysterious spores that alter her perception and make her immune to hypnotic suggestion. She feels a deep, almost unnatural pull toward the biological anomalies of Area X.

The Psychologist is the official leader of the 12th expedition, tasked with managing the mental strain of the team. She relies heavily on hypnotic conditioning to control the group's actions, memories, and panic levels in the unpredictable environment. She is secretive about the true nature of their mission, prioritizing forward momentum and control over transparency.

An unknown, shape-shifting organism inhabiting the depths of the structure the Biologist calls the tower. It creates a never-ending, biologically active script on the stone walls using a bioluminescent organic material. The entity serves as a central, terrifying mystery of the ecosystem, provoking both physical pain and intense scientific fascination in those who encounter it.

A former military operative, the Surveyor serves as the primary tactical and defensive asset for the 12th expedition. She carries the group's only assault rifle and views the bizarre anomalies of Area X strictly as physical threats. Her logical, surface-level approach to problem-solving puts her at severe odds with those who wish to study the environment.

A researcher assigned to study the structural anomalies and potential signs of human habitation inside Area X. She takes a cautious, methodical approach to her work, advocating for slow data collection rather than immediate exploration. Her careful nature makes her deeply hesitant to enter the strange subterranean structure discovered near camp.

A gregarious man who enjoyed boating, he volunteered for the 11th expedition into Area X before his wife joined the 12th. His highly sociable personality frequently clashed with his wife's need for isolation, leading him to nickname her the "ghost bird." He eventually returned from his mission fundamentally altered, possessing an unnatural calm that disturbed those who knew him.

An unidentified man who appears in a weathered photograph left behind at the region's lighthouse. He is depicted as being around fifty years old, wearing a fisherman's cap, and possessing a heavy face with a squinting eye. He represents a lingering historical question about the area before the border appeared.