The UAC is the first level of Doom (2016), and the player's first introduction to the UAC, Samuel Hayden, the demons, and the Doom Slayer. The mission that has you going through this level is called, quite appropriately, "Rip and Tear." You awaken from your slumber to find yourself surrounded by the living dead, and after taking them out and reclaiming your battlesuit, you learn that a demonic invasion is underway on Mars, and that the UAC facility has been overrun by Hellspawn. Time to do what you do best.