Take out the Big Gun sounded simple enough, except the Strogg were waiting. You, and a few marines like you, are the lucky ones. You've made it down in one piece and are still able to contact the fleet. The Gravity Well, the Strogg's newest weapon in its arsenal against mankind, is operational. With the fleet around Stroggos, 5% of ground forces surviving, and that number dwindling by the second, your orders have changed: free your comrades. Destroy the Gravity Well.

• New Enemies - The Stalker, Turrets, Daedalus, Medic Commander, Carrier, and the Black Widow.
  
• 14 Entirely new levels and 10 new deathmatch levels.
  
• New Power-Ups - Deathmatch specific power-ups: Vengeance Sphere, Hunter Sphere, and Anti-matter bomb.
  
• New Weapons - The Chainsaw, ETF Rifle and Plasma Beam.