It's a nightmare. You are trapped in an abandoned mine with an injured comrade at your side against God-knows-what. Make your stand, get out alive. Three words of advice: shoot to kill. These things are not human, they are monsters..
A great combination of zombie shooting and 'match-three' puzzling with an atmospheric (and bloody!) horror theme. Match up and pop the monster heads before they reach the barricade. Use grenades to get out of a tight spot.
You and a handful of others form the Last Line of Defense, pooling your remaining stockpile of weapons, special ammo, bunker defenses, and super-weapons to fend off the onslaught by virus infected, bloodthirsty Ravagers.