The Dark Mod Mod for Doom III Official SoundTrack, Vol. 1 addon

In The Dark Mod, you play a master thief living in a dark, sprawling city. A blend of gothic architecture and steampunk technology, the city contains great, belching chimneys, grand cathedrals, and medieval manor-houses. As a master of the shadows, you move through the city streets unseen, avoiding the eyes (and blades) of the city's thieves' guild, while doing jobs for the various political factions. Nobles, mages or the Church, it doesn't matter, as long as the pay is good.