This is it. The end game. After your pod arrives at the destination a Combine Elite takes the liberty of relieving you of your Gravity Gun. Bastard! Soon you are greeted by Dr. Mossman. Bitch! Your pod follows Dr. Mossman into Dr. Breen's office where he tries to coerce you into joining his cause.

image: http://www.hlfallout.net/image.php?id=31091 caption: Well look at that. The whole gang's here!

image: http://www.hlfallout.net/image.php?id=31092 caption: Dr. Mossman having enough of Dr. Breens ramblings.

And it seems like Dr. Mossman has had enough of his ramblings! She sabotages the door, spooking Dr. Breen who steals your Gravity Gun and tries to kill you with it, succeeding only in setting you, Alyx and Eli free. Judith Mossman takes care of Eli as you and Alyx chase down Dr. Breen.

image: http://www.hlfallout.net/image.php?id=31093 caption: Hey! That's MY gravity gun!

image: http://www.hlfallout.net/image.php?id=31095 caption: Hey! He's getting away!

You find him down the bottom of the lift talking to what looks like a giant maggot. He notices your arrival, drops the Gravity Gun and heads to another lift. After you pick up your Gravity Gun, Alyx soon discovers what he's trying to do and opens up the lift for you so you can chase him down.

image: http://www.hlfallout.net/image.php?id=31097 caption: The Dark Fusion reactor. The source of power for the Combine.

image: http://www.hlfallout.net/image.php?id=31098 caption: The Combine Portal.

Once you get down the lift turn left and you will see Dr Breen inside what looks like a massive bubble made of detergent. Take a right and head uphill, taking out Combine Soldiers and Elites with your Gravity Gun along the way and head to the three energy sphere 'chambers'.

image: http://www.hlfallout.net/image.php?id=31100 caption: Pull out these energy balls with your Gravity Gun.

image: http://www.hlfallout.net/image.php?id=31101 caption: Ride this platform up to the next level.

Remove the energy spheres with your Gravity Gun, hurling them at appearing Combine and continuing past the chambers to where a massive block is constantly rising and dropping. Jump on and ride it to the upper level.

Once you get to the top of the ride continue straight ahead and head out to the sparking end of the ledge. Here you'll want to save the game as it's tricky as hell in Normal and Hard difficulties. A series of small ledges make their way past the ledge and up to the next level which you need to get to. The catch is, the ledges are more slippery than a block of ice covered in oil. Don't crouch (it'll hurl you off if you do) just try and do your best to stay on.

image: http://www.hlfallout.net/image.php?id=31103 caption: To the left of this HEV dispenser is another lift going up.

image: http://www.hlfallout.net/image.php?id=31104 caption: And here it is!

After reaching the top of that terrifying ride you'll find another HEV dispenser. Stock up, take out the Combine which has just appeared, and take the next rising block to the left of the dispenser.

image: http://www.hlfallout.net/image.php?id=31105 caption: Take out the Combine troops and head left before you get to the door.

image: http://www.hlfallout.net/image.php?id=31106 caption: This is the last lift you'll need to take up.

Once you get to the top of this one more Combine Soldiers and Elites will appear. Take them out and head to the left of the door from which they appeared. Here you will find the last rising platform you will need to get to the top.

image: http://www.hlfallout.net/image.php?id=31107 caption: The portal is starting to open...

image: http://www.hlfallout.net/image.php?id=31108 caption: So to stop it, grab the energy balls with your Gravity Gun and hurl them into the reactor.

Once you get to the top the Dark Fusion reactor will power up, its petals opening up like a flower. Grab some energy spheres from the two rows of them just in front of you and start hurling them into the centre of the reactor. Eventually two Combine Gunships will turn up to crash your little party, but these are easily taken out by more energy spheres.

image: http://www.hlfallout.net/image.php?id=31109 caption: You can take down the Gunships with the energy balls.

image: http://www.hlfallout.net/image.php?id=31110 caption: Once the petals have opened up in the reactor, start hurling in those energy balls.

Keep hurling energy spheres into the reactor and it will start to fall apart. Eventually once you deal enough damage the reactor will shut down, trapping Dr Breen inside his giant bubble. But you've just destabilized a massive energy source and that sort of thing doesn't occur without consequences, which, as it happens, is the G-Man's favorite word.