The planned fourth add-on, which was advertised at the end of Nightmare IV, was to be hosted by Khufu. Though, due to poor sales, the game was never released and instead received an overhaul, which came to be Atmosfear 'The Harbingers'. In interviews with the creators of the series, they said production never began on the game, so no copies of it exist.
You shouldn't even be seeing this. Bizzeebeever told me to add this here so that we can get responsiveness working for all screens.