Makes Doom 3 into the proper hardcore survival horror game it should have been from the start. This mod makes the game much more difficult, but not impossible. Enemies are tougher, more aggressive, smarter and faster. Ammo is way less plentiful, and you will run out often. The sentry bots are no longer unstoppable, in fact you need to work together with them in order for you both to survive. The player is also more vulnerable, and if you are not careful, you will die quickly. This has been playtested from start to end to confirm that it is beatable, although barely.
One of the main things that bugged me about vanilla Doom 3 was the fact that they gave SO MUCH ammo, armor, and health all the time. There was little tension, because you didn't have to worry about running out of supplies at any point. This mod solves that problem, especially the ammo part. This mod will test your conservation skills as you try to make it through the game with limited supplies. I can't recommend this mod enough.