A guide to unlocking Rex legitimately for those having trouble.
How to Unlock Rex (Easy Method)
Beginning Unlocking Rex
Rex is a unique support role who can weaken enemies for your teammates and heals on hit. To balance this, most of his attacks cost health to use. He is an extremely powerful yet tricky character, especially late game where you can assist your teammates in defeating tanky enemies and even use his mobility power (skill 3) to shove healthy elemental enemies off of cliffs (and even a boss, the Clay Dunestrider).
Unlocking Rex requires transporting an equipment item, the Fuel Array, to Rex's body without activating it or dropping below 50% (in which case it will explode and instantly kill you). Supposedly activating it will also cause it to kill you, but I don't recall that happening when I tried to do so in my own run. Still, you couldn't hurt to be careful.
To start, grab the Fuel Array when you spawn. It appears on the back of your escape pod at the beginning of the game (and thus you can only get it if you or another player is playing a character who spawns from an escape pod, being any character besides Acrid and MUL-T). In addition, keep in mind that as the Fuel Array instantly kills you (with a small countdown) when you dip below 50% health, blood shrines will trigger the explosion if you activate them. Also try to avoid taking fall damage, as it can cause unpredictable and heavy damage.
You'll need to carry the Fuel Array all the way to fourth level, the red cave area (and you may wish to use a Newt alter to be certain you head to that level in particular). Rex can be found near some rocks towards the top of the cave (in the middle of the two cliffs you can only reach by using the water geysers). The location is shown below.
Once you place the Fuel Array into Rex, he will be unlocked as a character. This does not unlock him for your whole party, however, so each player needs to do this at least once.
The game will not let a player take a Fuel Array if another player is already holding one, thus you can only have one Fuel Array per playthrough. However, if you find an equipment barrel in the first level, the player with the Fuel Array can swap their equipment, let another player take another Fuel Array from an untapped escape pod, and then have the original player pick up the Fuel Array that was first dropped.
Handling The Fuel Array
The Fuel Array instantly kills you when you drop below 50% health. If it explodes, you lose it for good and need to start all over again. There are multiple methods to circumvent this fact.
- Have somebody carry it and stay out of harms way until the caves. If that player wants to unlock Rex, they can do so themselves (as Rex only unlocks for the player who placed the Fuel Array). If another player wishes to, the player holding the Fuel Array can pick up an equipment item to drop it for them.
- If you find an equipment barrel, you can temporarily swap the Fuel Array for a piece of equipment and pick it back up before you leave the stage. Items don't disappear over time, so you just need to remember where you placed it.
- Using MUL-T and swapping his equipment away completely negates the Fuel Array exploding if you drop below 50% health. Note that if you're below 50% health and swap back to the Fuel Array, it will explode unless you wait until you health above that threshold.
- Besides the above, playing Engineer is the safest bet given his defensive nature. Hiding away behind cover and your barriers while your turrets take the brunt of the force allows you to avoid tanking too much damage.
- Play on Drizzle. Rex does not need to be repaired on any difficulty, so you can abuse this to easily unlock him.
- If all else fails and you want to continue the run, you can avoid the damage from the explosion by doing any move that gives invincibility, such as using the Strides of Heresy.