Operation Hydra is a ZDoom wad I have been working on for about 6 months: it's been difficult, but I think it's finally paid off. Bear in mind that Hydra is heavily inspired by Ultimate Simplicity and some of Torm's work, so hopefully you dig that sort of style. :P If this wad proves successful enough I might document the adventures of the other two marines, so stay tuned. Go to the Zdoom forums to PM the creator about any issues or suggestions you may have.
Say, I remember this one from the /idgames archive (made by Obsidian right?).
It is a neat little mapset (About 3 maps if I remember correctly?) involving Trites from Doom 3 and a couple other non-vanilla monsters, all I could really say needs improving is a better ending room :P
What does the .deh file do here?