Demonbane USA is a desktop game installed on personal computers running Microsoft Windows. The gameplay takes place in Arkham City, a location populated by citizens employed in various industrial facilities that help keep the local economy afloat. Aside for its reputation as a center of intense economic activity, Arkham is also home to an educational institution called Miskatonic University. The school holds classes for students who wish to learn about arcane fields of knowledge and literary compositions.
The current economic stability and financial success of the city was led by a multinational corporate entity known as the Hadou Group. Hadou Ruri, a young businessperson, is one of the top officials within the conglomerate's ranks. At the same time, she is also responsible for maintaining the peaceful harmony of citizens living in the city.
The player then uses Ruri as a playable character in keeping the city in order by fighting supernatural forces that threaten the destruction of Arkham. Of the opponents that he player must defeat, the most powerful is Master Therion, whom the player must overpower by defeating his horde of minions. The gameplay moves forward when the user follows the story by completing certain missions along the way. Unlike other similar games, Demonbane is plot-driven, which means that most of the game is spent paying attention to what non-playable characters are saying.