Doom 3: Resurrection of Evil

Although the unnamed Marine of Doom 3 managed to stem the tide of demons through the Hellgate leading to Mars, the job remains incomplete. Two years after the events of that game, you take on the role of yet another unnamed Marine, who's tasked with returning an Artifact to Hell in an attempt to seal the border between the dimensions once and for all. GameSpot's Walkthrough gives you the details on the new enemies, weapons, and, of course, a complete walkthrough.