Collectibles:
1 Artifact
2 Logs
4 Weapon Parts
1 Blueprint
2 Upgrade Circuits

You come here from the staging area in Chapter 11 and see a Bench and a Suit Kiosk here. Use them to upgrade and stock up on MedPacks and Ammo and whatelse you might need.
Then grab the Unitology Artifact (2/2 (Chapter 11)) from around the corner, get the 2 Boxes and then take the elevator down to end up in a tram station with yet another Bench and suit kiosk. You can use the Skip to ride to other optional Missions, but this chapter here covers the Armory. And here is another great Scavenging Point for your little helperbot close to the skip, so drop it here.
Then take the elevator further down to the optional mission area to find 2 Ammo Clips to the left and yet another Bench. Maybe now you should switch the Probe gun you did build at the the end of chapter 11 for a weapon you are familiar with.

The get into the action, enter the first door down here. Get in the middle of the bridge and use kinesis to open the grates on both sides to get 3 Boxes and 1 Upgrade Circuit (1/2). The next room has a box on the left and the Stasis Amplifier Weapon Part (1/4) in a shelf behind it. And 2 Feeders are lurking around at the end of the room. As soon as you start shooting them 3 Slashers rush in and also attack you, so get rid of the Feeders really quick with 2 good aimed headshots and then take care of the Slashers. Finally it is time to open the 2 Lockers and take the elevator down, as we can't enter the other door yet as we are lacking the keycard needed.

The room at the bottom only has a cabinet, so continue, the room after that has some more goodies, 2 lockers and the Contact Beam Blueprint (1/1) behind it, and a cabinet on one of the pillars.
The next room though is filles with Feeders, there are 12 of them, get ready for tough shootout. After that get the 2 lockers and play the hacking minigame to proceed.
There is 1 Locker and a wall cabinet in the open next room. Through the door (you have to open) you run into 3 Slashers on the bridge. With Stasis they are really easy to get a hold of.
While the next room has a great Scavenging Point, the door malfunctions when you want to exit and you are ambushed by 2 Slashers, 1 Puker and 4 Feeders.

Over the Bridge you reach another room with 2 Ammo clips, an Audio Log (1/2) and an Upgrad Circuit (2/2). There is another door that needs a keycard, so we exit through the lift up again.

Kinesis the box to you to get it and open the wall cabinet, then walk along the catwalk. Of course you will be noticed, so shoot the Unitology Soldiers until the Feeder swarm attacks, then fight the Feeders of course. Take the cargo lift down and grab the Plasma Core Weapon Part (2/4), the 3 boxes, listen to the Audio log (2/2) and get the most important thing, the Armory Key. Once you got it all you will have to fight 5 Slashers coming from the vents from all sides.
Take the Cargo Lift back up and get into the elevator. When getting out you need to get into the locked door on the right, but slowly get there as another Slasher will jump out of the vent right there. Kill the Slasher and unlock the door with your new key and get in. Now you are under attack by 3 Stalkers, act clever and take them out. On a new game + there is an extra Upgrade Circuit right opposite the door. Get the box at the end of the room and also get the Unitology Artifact (1/1) at the opposite side behind a crate. Now you will need to play the shortcircuit minigame before you can proceed through the door. The solutions for the minigame were really close together for me on this one.

Now we are back in a room where we already were, but the cabinet is refilled. And once you try to exit though the main door you get locked in and ambushed again, this time by 5 Slashers and 2 Pukers. They can be a pain when they get too close. But after that we can continue through that door and take the elevator back up to the first keycard door we couldn't enter before but now we can.
In there 2 Unitology Soldiers shoot at you and even throw grenades, but they are not hard to handle, the ambush right before was harder. Open the 2 Lockers in the next hallway before entering the elevator. Up there you are in another tramstation where some whispering soldiers are around the corner. Once you get closer to them they start attacking you, but at the same time another Feeder swarm attacks them. Don't draw you gun to not attrackt the Feeders and hide where the soldiers can't shoot you and wait until they kill off the feeders. After some time they approach you so you just kill everything that moves.

Afterwards you can loot the crate in the corner for the following goodies:

• Acid Bath Weapon Part (3/4)
• Stasis Support Weapon Part (4/4)
• 1x Spare parts box
• 1x S.C.A.F parts box (is there any difference
• some more goodies

When you are on a new game + you can also nab another weapon part here, the MK-II Directed Ejection Field.
It is possible here to take the skip to the Supply depot when you haven't cleared that area before in chapter 9.
Before going back up chose wisely what you want to bring home. As soon as you take the elevator out of here it will be locked behind you and you are back at the area of the core drill. It is not that far back to the nexus, still you might be attacked by some enemies on your way.

So if you decide to get back to the nexus you will just enter the next chapter in the story which is chapter 12. Watch out for the ambush at the drill site and the head infectors after it.

But you can also get back to the staging area, get into the entrance of the armory and take the skip to the Supply Depot and do the optional mission there in case you haven't done it already back in chapter 9.
Please note that there are some new posessed Unitology Soldiers on your way back to the staging area, but also all the goodies are back in the areas, also the torque room (but it was lame the first time already and this time there is nothing but 4 boxes and a wallcabinet in there, so it is absoluteley not worth it). And there are 2 Scavenging Points on the way (in the empty way to the left into the mountains and right on the staging area).
Furthermore, everything you leave behind at the tramstation you just got locked out of, because your inventory is full, seems to still be there in the tram station under the staging area. Teleporting goodies sounds weird, but this happened to me.