Krauser
There are no enemies so far, but at corner are a bunch of enemies. Take care of them by shooting the red barrel between them when you're done - go down to the collect items. Inside the tend is a ladder to an underground path, collect items, meet a merchant and save before climbing the ladder and on to the next area. You'll be running into Krauser again and he will pop up from behind the rubble. From there, the monster will probably start throwing grenades at you or attack. He'll get down from where he's staying and attack you. Get to the west area where there are items and keep running away. With a bang and a flash, he'll disappear leaving you to rain the items in the room.
Head north with caution, one of the walls has your enemy waiting for you. Do the same process you did to get away earlier and then get to the east. The enemy will on top of another building and firing at you.. Wait for the procession of bullets to stop before running up the building forcing Krauser to jump down and face you. Chasing him away clears the path (as usual).
Holy Beast
Grab items that you need before heading east to where there are some rubble and a set of stairs at the top of the ruins. Get the first piece of the Holy Beast here and trigger another attack from Krauser. Equip your powerful weapons and blast away, keep doing this until he disappears. From where you are, push the statue onto the floor switch revealing two levers. One lets you backtrack to the last walkway leading you to a set of paths to the base of a tower. Climb the tower and search for some items where you get the second piece of the Holy Beast. Krauser will appear again and now you have a three-minute deadline to beat him. Get ready to dodge a lot attack, aim for the legs and when he's done pop some to his head. Do this repeatedly until he eventually dies, the third piece of the Holy Beast is on him. So take it and head to a path near the evacuation area and use the three pieces to open the door.
Helicopter Help
Make your way north and see the rescue helicopter arriving. Once that happens, more enemies will appear and the helicopter will shoot at the creepos for you. Now head towards the locked door to the NE and climb the first adder up the paltform. Open the locked door, and take out a chaingun wielding enemy before exiting the building via a rear door and get up the second ladder. If you haven't taken the chaingun dude down, from here you can easily snipe. Now when that's done, head to the north of the cam and get to a set of stairs leading to a zip line. Ride it down to the chaingunner's corpse and drop one level to unlock the door below. Get down agaIn and head through the door to enter another portion of the camp.
The door will lock behind you and another turret will start shooting. Get to the left and climb the laDder there and wait for the helicopter to take out another batch of mosters. Now to unlock the door in front of you,need two levers to pull open and they're all located at either side of doors of the balconines. The first one merely requires you to climb the ladder while the second needs you to backtrack to the small tunnel entrance you just came out of.