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INTRO: If you've already read this intro for a different ending, please skip to #1.
A few words about Sector 4. We will begin at the area labeled Page on the UPPER LEVEL. All these end maps (for Helios, Dark Ages and Illuminati) are the same except for the number placement; in other words, all word labels remain consistent. The Sector 4 map may seem confusing at first, but really makes sense as you explore the level and is very accurate. North is up.
There are three levels to the area, the UPPER LEVEL map on top, MID LEVEL map at lower left and LOWER LEVEL map on the right, which I've labeled on the map. You can basically stack each of these levels on top of another, with the central area on each being where Page is.
There are a total of three Universal Constructors on this map, one on every level, labeled in each case: UC-03, UC-02, and UC-01. Each one of these respawns any enemies you kill. On this UPPER LEVEL, there are a pair of spiders roaming the north corridor near the UC. On the MID LEVEL there are a few gray aliens. And on the LOWER LEVEL, there are several karkians and greasels way below. There are no more troops in the game, unless you are backtracking to Sector 3 or choose the New Dark Ages ending. When you're on any level, you are safe from the creatures on any other level.
Fortunately there's a great way to stop their respawning and defeat them as well. On the MID LEVEL and LOWER LEVEL you'll notice I put the labels "Bot". At this point on each level is a security computer terminal that you can hack to release a nearby security bot, which then comes out of its cubby hole and destroys all the beings on the level. It will continue to do so until it's destroyed, protecting you. After you release the bot, it's a great time to go over to the UC door, blow it open with a LAM or use your multitools on the keypad, enter the small room and turn the giant dial, which traps all the spawning creatures on the level, making it safe for you to roam around at your leisure. I strongly recommend doing this on both MID and LOWER levels. The spiders on the upper level will only have to be passed at most once, so no need to worry about the UC up there. Now on with the ending walkthrough.
1: Notice the four fireplace-like map locations at #1 on the Upper Level, #3 and #5 on the Mid Level, and #7 on the Lower Level. These are the fusion reactors you have to deactivate. You've already been transmitted three of the 4-digit code to do so, 724*.... You could figure out the last digit by experimentation but here it is: 7243. Once these four are taken down, you'll simply have to press a switch on the Upper Level to end the game.
2: From Page, take the south corridor, remembering to hug the walls around Page so as not to get hit by his EMP field. Take the small ladder up at the end of the corridor, go around the corner to the west, take the stairs down back to the north, and get to the #1 on the map. Use the code 7243 on the keypad at the reactor, and immediately crouch behind one of the crates nearby. There are two security bots deployed just ahead at the stairs that are programmed to take you out. Throw a LAM or EMP from behind the crates at the approaching bot to take it out, and then make a run for the left side of the stairway, out of the sight of the other bot at the top of the stairs. Toss another LAM or EMP from here to take out the second one, and then search the cubby's from which they came for a Hazmat, LAM and lockpick.
3: Head up the stairs to the lift at #2 on the Upper Level. Crouch/jump from the lift to a roof on the Mid Level, just above #3 on the map. Rather than jumping down, head west along the south wall to the map point labeled "Bot" at #4, hack the security computer terminal there to release the bot, and make the area a little safer from gray aliens when the bot takes them all out. Throw a LAM or bypass the UC door nearby the bot, enter the room and turn the giant dial to stop the spawning aliens from exiting the UC. You're still on the Mid Level near #4, so simply walk on over to the #5 fusion reactor. Enter the code 7243 and now it's just two left, another on this level and one below.
4: Proceed east around to the door north of #3. Open it, don your Hazmat suit and enter the radioactive room. The fusion reactor is in the back, so enter the code 7243 to deactivate it, and quickly run back out the northern door. Head to #6 on the Mid Level, overlooking the Lower Level and animals below.
5: If you have Cloak, now would be a good time to use it. From #6 on the Mid Level, jump down and hack the nearby security computer terminal which releases the nearby security bot to deal with all the karkians and greasels on this level. Now wander north and a little west to the UC door. Toss a LAM at it or bypass it, enter and turn the dial to shut the door to the UC, preventing any more spawns from escaping. Breath easier. Now head to #7 on the Lower Level map to the fusion reactor, enter the 7243 code to deactivate it, and then go to the lift at #8, pressing the switch to lower it if it's not already.
6: Take the lift up to the top and head north back around Page through the northern corridor at #9. Take out the spiders on the left as you please, or ignore them and run right (east) around the corner and then south. Labeled on the Upper Level map at #10 is the Nanotech Infusion Control room; it's a small room with a good view of Page and a single console with switch. Simply hit the switch now and witness one of the three endings of Deus Ex. Congratulations on beating one of the best games of all time!
