Ares Magazine #15. Nightmare House is a two to five player game of ghost hunting and exorcism. (There are solitaire rules). One player (the House) takes the role of the Evil Entity that has spun its web of power over the Darkholm Manor. The other players (called the Hunters) each represent a ghost hunter who has entered the house one dark night to confront and banish its evil.

The battle against the House takes place on two planes. On the Astral Plane, the Hunters try to reach and exorcise the Entity hidden in the heart of darkness of the House. The Hunters must advance along the 12 Axes of Power, weakening the House and destroying its web of evil by exorcising the Entity's power from individual rooms in the Manor. The House tries to trap the Hunter's Psyches and cast their Astral bodies adrift on this plane.

On the Material Plane, the physical manifestation of the House, the Hunters search for discoveries to help them on the Astral Plane, as the House materializes Physical and Psychic Haunts against them through its Foci of Evil. The House tries to take possession of the Hunter's physical bodies, destroy them, and absorb their souls. The Hunters use various tools and strengths to defend themselves against the Haunts.