
Back in 1996 or so, I started a project for a doom prequel called B4DooM (before doom). Some of you might know it from geocities - it ranked #7 of over 3000 doom mods at one point by some place I can't remember

I saw it one day on a hard drive backup and thought I would see how the ports are doing nowadays, and was pretty impressed. So I've decided to ressurect the project. I have to start pretty much from scratch though, because the last project used gross hacks and so had some pitfalls. This will be cleaner and more special than before.
The prequel combines the plots of doom and heretic/hexen, where you play as the sorcerer d'sparil, who was banished into hell but escaped with the new slipgate technology - unleashing the monsters onto mankind once again.
The gameplay is obviously different, more warlike and not a matter of finding keys and exits - but rather killing all marines and possessing them into the zombies and using their souls for health, weapons, powers, and to summon/ressurect other monsters to attack the others. All current monsters in the doom game are on your side and the possessed soldiers are still marines. You are more powerful than the doom player - you can fly, have magical weapons, more speed, more "health" and demons on your side - but the marines are more powerful than many of the original doom monsters and have rocket launchers, plasma rifles, BFG9000's... so the battle is not completely one sided.
Although the previous project was quite developed, this one is in a very early stage, and has alot of further potential (a cool intro, scripts showing the demons impaling marines etc after the battle, making cyber-monsters etc).
There is a strong focus on commercial-level quality and a philosophy of keeping it close to the original doom game - meaning no sprites, sounds, or 3d models etc that look too different to the original or levels that are too complex. It is not about making the doom engine more than it is (it will never match current 3d games), but enhancing it to feel like it was how it was supposed to be.
I put up a blog to introduce it. No downloads are available yet - but if you'd like to contribute something by all means let me know!
http://b4doom.blogspot.com