In order to shut down the link between our dimension and Hell, you’re going to have to ferry said artifact back to where it came from.
It doesn’t take long for yet another invasion to occur, but this time, it’s triggered by the discovery of a powerful artifact. After the events of Doom 3, wherein UAC’s Mars labs were almost completely overrun by demons coming through a Hellgate, they’ve unwisely decided to set up shop on the red planet once again. The ending to Doom 3 made it clear that there was unfinished business left to be tended to in the depths of Hell, and Doom 3: Resurrection of Evil puts you in the shoes of the Marine who’s going to handle it.