The Ultimate Doom

Ultimate Doom is an upgraded version of Doom released in 1995, adding the fourth episode Thy Flesh Consumed. The only other changes to the game itself are the addition of a few passages in E1M1: Hangar and a secret switch in E1M8, which were added to allow for more interconnected deathmatch play. The executable packaged with Ultimate Doom imports some editing features from Doom II, including a new sector type and 37 new linedef actions, which among other things allow for "blazing" doors and keycard switches.