Find a Way into the Dig
Set your quick-swap to your suppressed Handgun and Assault Rifle. That combination has been working very well for us, allowing for split second adjustments when things go sideways. When you're ready to move, sneak forward and take the path to the left, through the tombstones. This should allow you to score a headshot on the Commander that is in the guard tower in the middle of the yard. The second Commander is a little further forward, sitting in a guard shack that you can reach by maintaining your current course along the left wall. Use your Signal Detected if you're still not sure, taking him out with a suppressed Handgun round to the skull.
Backtrack out of the guard shack and back the way you came. You only need to go a few feet, locating a small building with a hole in the floor. Drop through the hole, then follow this path until you emerge at some scaffolding. Climb up, then press forward until you reach an electrified door. Objective complete.
Sneak forward and put a knife in the lone guard on patrol, then continue on to find two more up the stairs on the left. They can be dropped with well timed headshots, but you have to watch out for the Supersoldier who is roaming about nearby.
With those guards down, allow the Supersoldier to turn his back and walk away from you, then quickly sneak behind him. We're serious. Follow him down the path, then duck into the alcove on the left when you can. Allow the Supersoldier to turn and walk away again, then press forward and use the elevator to head further into the mines.
Hop off the elevator to find a Signal Detected, as well as another Supersoldier roaming about. Wait for the big metal jerk to turn his back, then sneak forward and turn into the cave on the left. You'll come to a dead Nazi with armor (which you should take), which is your cue to turn around and use your Pipes to climb the nearby wall. Be very careful about this, as there is a Nazi Commander on the ledge. Quickly move up and put some bullets in him before her spots Blazkowicz and sounds the alarm. Drop back down, then continue sneaking through the tunnel until you come to another electrified door. Turn the power to the door off and head through.
The Nazis on this side are busy with something, so take a moment to pop them in the skull, cleaning up any that might turn into Nazi zombies. When the area is secure, head further down and climb through a small opening in the wall (it's marked with an objective marker).
Move through the tunnels, fighting your way past Nazi's and zombies. You really only have one way to go, so just keep grabbing loot and ending lives. When you reach a giant hole with a spiral staircase going down, begin your descent, jumping into the water and then climbing back out and up the ladder. You should hear Helga at this point, so squeeze through the cliffs, then go for another swim to reach an a button marked as your objective. Push it to activate the door.
Before you can go through the door, you'll have to spend some time taking out the Nazi zombies that are attacking you. There's no way around it, this section is designed to make you fight. It's an easy fight, but you're going to have to spend a bit of ammunition just the same. In our case, we used up all that we had with the Sawed Off Shotgun, and even got some Pipe action in while waiting for the door. When you can slip through, resupply as best you can, then continue forward to the final boss fight.
Defeat the Monster
There are two key things that are important to know if you're going to defeat this thing. The first is that it's blind, so as long as you aren't making any noise you are (relatively) safe. The second is that the weak point is the beast's mouth, so to defeat it, that's where you'll have to concentrate your fire.
In terms of what to expect when the monster does attack you, there are three things it can do. The first is to slam one hand down, the second is the (upgraded?) two-handed slam, and the third is a sweep from one side to the other. As time goes on in the fight, this sweep will turn into a clap, and we're pretty sure that Blazkowicz should avoid being in the middle of that finale.
At a certain point (fairly early in the fight) you'll have to deal with Nazi soldiers, but the best way to do this is with your suppressed Handgun. They are shooting big, loud weapons at you, so the monster will attack them. By using your suppressed Handgun, you kill some, while the noise they make trying to kill you prompts the monster to go after them.
Tip: Throw grenades at the Nazis that attack, as it makes no sound to throw, and when it does explode, it will draw the monster's attention to where it detonated.
That's basically it. Shoot the monster in the mouth, then relocate before he can squash you like a bug. When the Nazis show up, let them kick up a fuss so that they become the beast's target. When the monster falls, you've beaten Wolfenstein: The Old Blood.
Feel free to return to our Wolfenstein: The Old Blood walkthrough.