• Spacesuit Helmet--Base 2B
  
• Spacesuit Chest--Base 4
  
• Spacesuit Trousers--Tunnel 2A
  
• Spacesuit Backpack--Tunnel 6

Miner's Helmets and High Vis Jackets are possible, but they aren't static.

• Letheia Corporation Guidelines--Tunnel 2A
  
• Communication Failed--Base 4
  
• Emergency Lockdown--Tunnel 6

This is in Tunnel 6. The switches are in Base 2B (Morphball) and Tunnel 6.

The most important requirement is to have all three basic techs unlocked. Dashing isn't very helpful for range warfare, but pulse jumping is, and morphball is good for getting all the loot. If you can find tier 2 armor, great. If not, just use your Iron Armor. If you have found any guns, bring them along. If not, craft some hunting spears (a few hundred ought to be enough) and/or a hunting bow at your foraging station. You should also bring along some salve and any bandages you can find. A shield is very useful, but you may not need it for range warfare. If you want to get to the secret switches, you'll need climbing rope (a few dozen to be safe) and the morphball tech. You don't need to worry about emptying your inventory in Survival Mode, since no items are dropped on death in a mission. Instead, the mission resets itself when no one is in it. (There is one checkpoint close to the boss.) You don't even need to bring food--your hunger bar freezes when you deploy.

There aren't any enemies until after you flip the breaker. Activate the consoles to turn on some lights. The area to the left has beds and lockers.






Between the ladder to the beds and the bathroom ladder you will find a crate and a water cooler. Go right and follow the ventilation to get around the locked door.





When you flip the switch, a Moontant (40HP) will fall onto the nearby pile of rubble. Try to stay away from his erchius goop attack. (You may be able to detect the charging animation.) Two more Moontants fell down onto the water cooler. After killing them, descend into the mine.

The door on the left is controlled from the other side. You can use it to let your friends through in multiplayer. The door on the right leads to a stretch with seven Moontants and three crates. You can use the door to kill the first few. (Open it, shoot, and close it. If you have non-limited explosives, you can attract them to the door and blow them up through the door.) After the girders, you'll find three more Moontants and a switch. The switch reveals a miner, a Moontant, three chests, and another switch.
This switch drops another Moontant on the crates and opens the hatch. After descending the shaft, you will find more Moontants on the left. They can hit the bottom girders, but not the second tier.

There are five Moontants guarding this shaft. If you keep going left, you'll encounter Base 2B and skip some of them.






If you go down, you'll encounter three more Moontants below guarding a chest with Spacesuit Trousers and the Letheia Corporation Guidelines. Back to the left, you'll have to kill three more Moontants to reach another door. There are six Moontants beyond the door, with four of them in range for the door-shielding tactic mentioned above. When you approach the crates, the five Moontants patrolling above may see you. You can attack them as they descend or rush through and pulse jump onto the handy platform.
If necessary, you can run to the right and pulse jump across to the chests for a little rest. If you have Explosive Burst on one of your weapons (or sticky grenades), you can attack the eight Moontants on the platform above from below. If you go right from there, you'll be at the exit to Base 2B.

Coming from the right, you'll find two Moontants between the first door and the entrance to the base. There are four Moontants and some miners inside the base. The chest under the base has the Spacesuit Helmet.




If you climb up the left side of the base and use morphball to go right, you'll find a shaft above the skylights. Use climbing rope to get up and flip the switch. If you haven't killed the eight Moontants to the immediate left yet, do so now.

At the start of this section, you'll find a door. It doesn't do anything except protect you from Moontants if you hide behind it. There are three Moontants guarding the stairs.





The switch above opens the door you saw much earlier.

There are three Moontants in here. Once again, you can climb the left side and get through ventilation. This leads to a chest with the Spacesuit Chest and Communication Failed. Continue to the left until you spot a hazard sign above a switch.

When you activate the switch, you will open doors to the right and left. To the right is an Armored Moontant (120HP, 10 Armor). You now have three choices.

1. Fight him now. (Not reccomended for Iron armor. Do this only if you have a shield.)
   
2. Run to the left, flipping switches as you go until the miners help you. (Recommended if you don't have pulse jump available.)
   
3. Pulse jump up to the hazard sign and snipe at him. (Ideal. Rising Slash can substitute for pulse jump.)

Once you defeat the Armored Moontant, rest up in the bed and visit the checkpoint. Once the dish starts rotating, you're good.

There are two more Armored Moontants in here, one above and one below. You can lure them back to base 5 and kill them the same way you killed the first one. (Note that you now have space to dodge the hammers if you want to fight melee.) The upper one was guarding a chest with the Spacesuit Backpack and Emergency Lockdown.
If you look above the small girder, you'll see a large hole. If you move your camera as high as it goes and jump, you may be able to see the platform with the second switch on it.





You'll need to grapple with the right wall, jump, and grapple with the left wall above the switch in order to reach it. (You might want to bring a friend with the rocket jump tech to reach it easier.) Alternatively, you can use the spike ball tech to just climb the ceiling. If you don't have the grappling hook or spike ball tech, you can equip a dozen ropes in each hand and then climb around from the left.
Once you go down the stairs, you'll encounter another door. There aren't any enemies immediately beyond this one.






Keep going left to find a morphball tunnel. If you flipped both switches, the symbols inside will be glowing and the hatch to the left will be open.






The chest below has the Left Translation Wheel. If you aren't at full health, now is the time to go back and heal before descending the shaft and entering the boss chamber.

The boss chamber is effectively set up in a circle. At the center is the Erchius Horror. Below is a Laser Cannon. On either side are two switches (four total) with orbs above them. To defeat the boss, you'll need to activate all four switches (turning the orbs blue) and then activate the Laser Cannon. After firing, you will need to repeat that twice more. At the same time, you'll have to dodge the Erchius Horror's plasma lasers. They follow a pattern: two lasers rotating clockwise before the first hit, four lasers rotating clockwise then counter clockwise then clockwise until the second hit, and four lasers making flapping motions (>< to X) until the final hit. After completing a laser cycle, a Moontant will spawn from the Erchius Horror.

When you first enter the chamber, drop down and flip the switches on the left, then jump up, go right, and flip the switches on the right. If you're fast enough, you can fire the Laser Cannon before the cycle finishes. For the second hit, flip the left switches (or right switches, sides are arbitrary form here), then wait for the cycle to end (or rush through with a shield, preferably pulling it out right before you go through), run to the right and flip those switches, dodging the moontant. For the last hit, you'll want to run left and get as far as possible before the lasers turn on. There are safe zones in the four cardinal directions.

After you kill the Erchius Horror, you can kill the Moontants and talk to the miner. The chest beyond the door has The Erchius Horror codex, pixels, a tech card, and two capture pods. If this is your first time through, it will also have some weapons. Be sure to activate the drill to get your Erchius Crystals before you teleport out. Congratulations! You have completed the first mission.