Acid Sanctuary is the first map of the Realm of Blacksmiths in Dimension of the Machine.
- On the starting platform, go down to the lower part of it and go around the left side; you will eventually spot a large Box of Shells.
- On the large skyway containing the two switches which require the Gold and Silver keys to operate, face the way you came and jump on the stone railing to the right of the staircase; there is a narrow edge around the tower you can land on. Down here is a path that leads to 2 Boxes of Nails and 1 Box of Shells.
- Inside the room containing a group of Knights and Death Knights, deal with them, then go to the stepladder on the other end of the room to head to the upper level, on top of the crumbling/incomplete platforms. If you look to the right side, you will see that the very end of the path has been gated off. You can jump on the edge of the stone column right next to the wooden planks that obstruct your path and carefully walk around it to get to the other side to find a Yellow Armor.
- You will eventually find yourself inside of another incomplete-looking tower with a set of locked doors on the first floor that must be activated via a button on the top level. On the lower level will be a Fiend hiding around the corner and on the top level will be a duo of Knights guarding the button. On the side of this upper level opposite the button there is a narrow side path you can drop down to find a 100 Health. Grabbing that will lower the wall in front you, bringing you back to the lower level of the tower you were just at.
- There is a narrow bridge/scaffolding guarded by 2 Scrags and a ledge on the other end containing a button. Pressing this button displays the message "Shortcut opened" and a small elevator will then come down to lift you up. Going up this lift, you will see another ledge across from you with a giant yellow pipe of sorts running down it (along with another Scrag or 2); jump down to this new ledge and look to the left, just behind the pipe to discover a broken/tilted tower that you can jump inside. Doing so will net you a Grenade Launcher.
- You will eventually find yourself ascending another piece of what seems to be scaffolding or a small set of wooden stairs that leads you up to a duo of Death Knights. Before going into the window of the tower just in front of you, look to the left to spot a sizeable gap in the small wooden bridge connecting the tower the Death Knights were on to the other, bigger tower where the open window is. Drop down here to find a Super Nailgun.
- In the outside area with many giant yellow pipes, press a button to raise up a metal slab next to a giant fan which contains the path you need to take to continue with the map. However, before dropping down to it, there is a narrow ledge to the left of the button that you can walk around. When the ledge ends, there is a fairly tricky jump you can make to an alcove on the left wall containing a 100 Health.
- Near the end of the map, you will find yourself ascending a giant tower that is tilted and broken in several spots. At the very top of the tower you will see a bridge leading into another tower as wall as a giant wooden windmill. There will be a Death Knight and an Ogre up here as well. Look behind you, across from where the Ogre was, and you should see a large Box of Nails (if you haven't picked them up already); there is a large portion of the floor here that is missing, which is a shortcut down to the lower levels of the same tower. Drop down to the closest level of the tower below you and walk around to what seems to be a pitch-black corner with nothing in it. There is a Red Armor waiting for you in the shadows. The armor is nearly invisible until you get closer to it (depending on your brightness settings).
- Go back to where you were when you accessed the previous secret, only this time actually go into the tower next to the windmill. Drop down to the bottom of the tower (beware the Spawn hiding under the staircase!), head to where the 100 Health is and then immediately look left. There is a large pile of bricks leading to a higher-up platform, containing some Zombies. Jumping up the bricks will lead you to a tilted tunnel containing some more Zombies. At the intersection here, go straight down the ramp into the pool of water below, look to your right and surface to reach the platform containing the Rocket Launcher that you may have spotted earlier on.
- To the left of the Gold Key button (on the main bridge in front of the big gate where Secret #2 was discovered, jump up on the left-hand rail to spot a couple of pillars to your right as well as a broken part of the fortress; you must jump from the railing to the top corner of the aforementioned fortress, and then jump from there to the higher-up pillar in order to reach the floor teleporter at the far end. Doing so will teleport you to a high-up platform opposite the Gold and Silver Key Buttons which contains a Quad Damage. It is best to save this secret for last, as once you activate both buttons, a group of enemies (including Ogres and Vores) will spawn all around you to try and ambush you. Saving the Quad Damage for this fight will make it a breeze.