The Carcadia Burn Vault is the second special dungeon you can explore in Borderlands 4 — but only after you have found its three key fragments.
Also known as the Vault of Radix, the place is similar to the Fadefields Vault, structurally speaking. However, the boss in this Vault offers a completely different fighting experience, testing your overall awareness of the battlefield and capacity to keep causing damage.
If you’re ready for this challenge, we can help you. In this Borderlands 4 guide, we explain where to find the Carcadia Burn Vault key fragments, where you must go to activate the Vault door, and how to beat Radix, the final boss.
Carcadia Burn Vault key fragment locations
Fragment #1 location
You can find the first Vault key fragment in the Yawning Yard in the Lopside region. To quickly reach where the fragment is, travel to the Makeshift Chalet Safehouse. From there, go south to find a building with a long corridor in the upper part.
Climb the walls and enter this corridor to find a dinner table. Your first Carcadia Burn fragment will be stuck in the middle of it.
Fragment #2 location
The second key fragment in Carcadia is located in the Wreck of the Last Great Hope area in the Tonnage Peel region, west of the Lowrise Safehouse.
First, you need to access the underground tunnels in the area. There’s more than one entrance, but the one in the south is the quickest one to locate. Once inside, turn right into a short corridor with a red light.
There’s a small door on the ground you can open using the grappling hook. Go through it to fall into a cave where the fragment is hidden.
Fragment #3 location
Travel to the Ruined Sumplands area to find the third and final fragment. The quickest way to get there is by fast traveling north, starting from the Judgement’s Lapse Silo.
Once you arrive in the area, head northwest to find a body of water on the lower level. Turn right and look for some golden spheres in the walls. The key fragment is below one of them.
Carcadia Burn Vault door location
With the three key fragments in your inventory, it’s time to find the door of the Carcadia Burn Vault.
You want to fast travel to the Grindstone of the Worthy region by using the Rustical Hurl Silo if you have unlocked it. The door is north of the Silo, close to where the Vault icon appears in the middle of the blue circle.
Look for some debris on the northwest side of the region. The altar is hidden, and it will only emerge when you get closer to where it’s located.
How to defeat the Primordial Guardian Radix
The fight against the Primordial Guardian Radix requires attention and consistent management of your dash charges to avoid the boss’s attacks. Radix lacks explosive skills that could kill you with a single hit, making it a less punitive boss fight.
During the whole fight, pangolins will spawn and run after you. It doesn’t matter how many you kill — they’ll keep coming back. They are regular enemies who can’t deal a lot of damage, and, as happens in Borderlands 4, they are meant to be weak targets to help you get on your feet when in Fight for Your Life mode.
Another general note about this fight is that Radix has an energy shield, which you can destroy faster when using electricity-based damage. The boss is always two levels above you, so the damage it does is always balanced based on your level.
Below, you learn the boss’ moveset and how to deal with each situation:
- Flying rocks: Throughout the fight, Radix will smash the ground and make some rocks start to fly around it. These are meant to work as an extra defensive layer, since you will have trouble getting near the boss. Later in the fight, Radix amplifies the radius of this attack, placing the rocks next to the limits of the arena.
- Shockwave: Usually, Radix follows up the pillar attack with a sequence of four shockwaves. It punches the ground, sending electric waves that cover the whole arena. The best strategy is to stay on top of one of the rocks the boss created with the pillar attack.
- Shooting rock: Occasionally, the boss lifts its left arm, charges a rock with electricity, and shoots it at your current location.
- Jump attack: After digging a path underground in the arena, Radix will jump at you and try to hit you with its modified left arm. Run or dash sideways to avoid the attack, but be sure to be a safe distance since the boss’ attack hits the area around the point it lands.
- Underground attack: When Radix deactivates its flying rocks, it may perform an underground attack. While avoiding this attack is quite simple, since the boss rarely goes to where you are located, you’ll need to pay attention to the trail of bombs it leaves on the arena.
- Tempest: During the fight, Radix may go to the center of the arena and charge its body with electricity. If you see this, it means the boss is going to start summoning lightning in several places in the area. You can avoid them by paying attention to the blue marks on the ground, which indicate where the lightning will hit the ground. Dash out of the attack if you find yourself right where the lightning will land.
Responding to most of these moves depends on being in constant movement during the fight and knowing when to glide and dash. By spending your backpack charges at the wrong moment, you may find yourself having no way to escape a giant rock flying toward you. The best practice is to hold the dash charges for emergencies.
After being defeated, Radix drops several weapons, Eridium, and cash — in addition to two red chests you find before leaving the dungeon. We faced it at level 40 in the Ultimate Vault Hunter Mode rank 2, and we earned 2,552 experience points for killing it. Completing the Carcadia Burn Vault for the first time gives you an upgrade to your backpack by reducing the regen delay.
Do you need more help with Borderlands 4? For those who are new to Kairos, check out our beginner’s guide before you get started and our best classes guide to find the right one for your playstyle.
If you want to have fun with your weapons, be sure to read our guide on how to get more SDU tokens. We know that traversing the immense map of Kairos is a challenge in itself, so you should prioritize unlocking a vehicle, as well as fast travel points. And if you’re already enjoying the endgame of Borderlands 4, don’t forget to check the weekly reset time for all current challenges.
