Sinful Influx mod for Doom

The Story So Far...

Years after the invasion of Phobos, all was thought to be peaceful. The moon was under military purgation, and the Mars colony was finally settling in place after the horror that took place up there. It seemed as if everything was at rest. However, in an underground UAC complex in a remote region on Deimos, trouble was stirring. Written reports of maintenance workers mysteriously disappearing were piling up on the administrators' desktops. A majority of the reports described the crew seeing strange "pink" gorilla-like creatures, sometimes even being attacked by them. The security team was sent down to investigate the disturbances, but days later, none of them had returned. It was time to call in the bigger guns.
You're a marine, from one of Mar's finest military establishments. You were sent up to Deimos with one objective in mind: to descend to the reaches of the same underground complex where all the activity was reported, and eliminate the threat. You board the shuttle with five other top-notch specialists that you'll be working with in the duration that you're there. A computer technician, three combat specialists, and a medic. If you work together on this one, it shouldn't be such a hard task. You've dealt with terrorists and suicide-bombers before, so why should this be any different?
At twilight, the shuttle arrives on Deimos, and you are greeted by the director of maintenance. He leads you and your buddies to your crew quarters and you prepare for the next morning. Too bad you have no idea what you are getting yourself into... a simple joyride might possibly turn into an one-way elevator ride, straight to the depths of Hell.