Not an add-on for Atmosfear, but a game in it's own right. The Third Dimension was released on PCs around the world. It was mostly a remake of Harbingers for the computer, but it did have some differences. The game also came with a soundtrack that was meant to be played along with the game. There have also been rumors of an expansion that was released in certain countries that allowed play over the internet, though noting has turned up to prove, or disprove this.
Approximate Running Time: 30-80 minutes