The gameplay and mechanics for the Underdome is very simple, there are rounds and each round consist of 5 waves with the last wave being the boss wave. With every passing round the difficulty is increased.
F.E.A.R. 2: Reborn gives you the opportunity to experience the events of what transpired in the original game from a different perspective. You take on the mantle of Foxtrot 813, one of the Replica soldiers. Shortly after arriving in a kick ass Power Armor Suit to offer back up to your squad you start hearing a voice.
The enemy AI is even deadlier than before, they actively find better methods to pin you down so that the other half of the squad can flank and kill you. There are a variety of world items that can be interacted with to help aid you; such as creating instant cover for example.
You start the game with your eyes all foggy until a few browns rub some acid into your eyes to get them to focus properly. Once that has been done, Gnarl slowly starts introducing you to the life of an Overlord