REX is the secret survivor to unlock in the game. Unlocking REX is extremely difficult and also involves a few random elements to align in the game. This guide will breakdown the details on how to unlock REX and finish the “Power Plant” achievement.

Getting the Fuel Array

Fuel Array Drop Pod

The first step in unlocking REX and finishing the “Power Plant” achievement is by opening the tiny compartment behind your escape pod to get the Fuel Array equipment as you spawn in the first stage of a playthrough. If you are playing solo, the challenge is not possible when you start with MUL-T or Acrid because you will not start the game in an escape pod.

The Fuel Array will take your equipment slot until you finish the challenge and remember to never use it or it will activate a timer that will kill you instantly. Reaching 50% health will also automatically activate the timer and kill you. This is the main obstacle you have to go through. You will not be able to use any Blood Altars or it will activate the timer and kill you.

The best way to overcome this challenge is by getting the Transcendence lunar item which turns your health into shields. Basically, you will be running with 1 health at 100% but have enough shields to work with. This will negate the challenge the Fuel Array brings to the table aside from taking an equipment slot from you.

You can also swap this equipment around during the stage but do not forget to switch back to it before entering the teleporter. This is a great and safe strategy to do when you do no have enough survivability yet. The only downside to this is you have to spend gold on equipment barrels every time and not use it.

Finding the Abyssal Depths Environment

Abyssal Depths Fuel Array 1

After learning about the Fuel Array equipment, you will now need to look for the Abyssal Depths environment. Keep playing normally and safely through the stages and wait until you find the Abyssal Depths. If you are not able to enter the Abyssal Depths environment in the first four stages of the playthrough, you should restart the game already.

This is because the map cycle will always be the same for the first five stages where the 5th stage is fixed at the Sky Meadows environment. Abyssal Depths is rarely than usual so it should take a few times before it shows up. The most difficult part of this challenge is getting here.

Finding and Repairing the Broken Robot

Power Plant Fuel Array 1

Once you finally reach the Abyssal Depths environment, you will need to find a broken robot somewhere on top of the cliffs in the environment. Surprisingly, I have seen this achievement finished 3 times through my playthroughs and it was always at the same cliff. You will use the Fuel Array to repair REX and you will earn the achievement.

As you spawn in Abyssal Depths, exit the cave and immediately hug the wall to the right until you find the long ramp leading you up. You will find a long chain you can cross to get to a cliff near the middle of the stage. Now that you are on top with a great view, find a boost where you get propelled even higher or into another cliff. Keep checking the cliff and you will eventually find the broken robot which is REX.


This challenge is quite difficult but also exciting at the same time. Dropping to 50% health is basically playing with a Shaped Glass without the damage bonus. Make sure you bring your best survivor aside from MUL-T and Acrid when finishing this challenge. I suggest going for a ranged survivor that can deal high amounts of damage with fewer items.