I've now included a separate "Nightmare" addon for more variety of monsters.
Added Ghosts & mini-bosses in the optional addon, zombiePLUS mutator (9 new zombies) and provided ways to disable various optional creatures or to replace zombies with the Swarm.
Added compatibility patch for Zero Tolerance and Neocore for their zombies or marines to show up when you use them with this mod (see load order).
Download: http://www.moddb.com/groups/doomdb/addo ... -doom-v112
My Intentions - To make the game more difficult while retaining the dark theme started by DMG Heretic's mod, the Nightmare addon adds enemy variants, its optional so you don't lose the classic feel. In case you don't like the GasManacubus or the Pain Elemental that vomit's bile, heres a older version (minus the weapon changes by DMG Heretic so its still compatible with weapon mods). Or you can get the original version by DMG Heretic that has the 2 weapon replacements.
Load your preferred weapon mods, then the main DMG1.1bx file, the addon third, and mutators and/or compatibility files always last. Make sure to only load one zombie (or swarm) related mutator since they overwrite the same spawns, and one nightmare (or mini-boss) mutator. You can always load NoNewPowerups or NoNewBosses.
The addon is optional but adds many creatures including, 8 more zombies, 2 additions to Imps, one for Baron, Caco and 2 for Mancubus, various Lost Souls and Pain Elementals, Ghosts (that are semi-common for low level monsters like imps/beasts) & mini-bosses (rare spawns for Baron, Spectre, Mancubus, Archvile). All spawns can be tailored to your taste with the mutators.
Previous changes (by [DMG] Heretic):
Dark Doom v1.1 - I have removed PSX SFX & kept every Enemy/ weapon to Doom's original SFX & also re-coloured the Archvile to a Dark Version and The Revenant has been replaced with a stronger/faster Death Imp.
Dark Doom v1 - Enemy replacements, & PSX SFX.
Screens (the first 8 have Weapons of Saturn hud/weapons, but you can use any weapon mod you prefer, the rest show the dark hud)