Fallout 4 Crucible guide and how to get Ballistic Fiber

fallout 4 crucible
(Image credit: Bethesda)

The Fallout 4 Crucible quest needs ballistic fiber and it's almost certainly why you're looking for help, unless you already have plenty sitting around. The bulk of this quest is fairly easy - go to Saugus Ironworks, kill everyone, and pick up the heavy incinerator reward. However, to do that, you'll need to mod some power armor to be flame resistant. That needs ballistic fiber, and that's the main sticking point in this quest.

So, let me walk you through the Fallout 4 Crucible quest, and show you where to find ballistic fiber to finish it.

Fallout 4 Crucible walkthrough

fallout 4 crucible location

(Image credit: Bethesda)

The Fallout 4 Crucible quest starts with the objective to Investigate Sangus Ironworks in the North East of the map. When you arrive you'll have to battle members of the Forged faction to get inside, and then more again once you're through the door. 

The objective marker should lead you where you need to go for most of this stage. If you can't hack the advanced terminal to open the door to the second part of the building, you can keep heading up and use gantries in the rafters to pass over. 

fallout 4 crucible Forged Keeper

(Image credit: Bethesda)

There will be more Forged to kill, but the objective will reveal itself to be a boss enemy called the Forged Keeper. Kill everyone and then check the Forged Keeper for the Forged Keeper's Note, which talks about a heavy incinerator and directs you to a tool box where you'll find the Forged Recruit's Note. 

This will explain the Forged trial - walk across a... crucible of molten metal to pick up the heavy incinerator. But before you can do that, you'll need to stop the flow of molten metal to reach some items you need. So follow the objective markers to turn off the molten metal flow control, and then use the terminal to move the crucible.

With the crucible out of the way you'll be able to pick the gear: a set of raider power armor legs, mods and some military duct tape. Now here's where things get tricky, because to craft the flame resistant mods required to reach the incinerator you need the following resources:

  • Adhesive x5
  • Asbestos x6
  • Ballistic Fiber x6
  • Rubber x3

At this point you can mark the recipe requirements for search, so that anything that has what you need is highlighted by a little magnifying glass when you look it. Most of this is easy except for Ballistic Fiber, which is the problem resource here. Below, I'll cover two ways I've definitely found Ballistic Fiber. 

Where to find Ballistic Fiber in Fallout 4

fallout 4 crucible resources

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You can find Ballistic Fiber in Fallout 4 in Military Grade Duct Tape and Military Ammo Bags. Both are hard to find. However, you'll notice you get three rolls of Military Grade Duct Tape with the buried power armor parts. Each breaks down to get you two units of Ballistic Fiber, which in total is enough to get you the six needed to mod one leg. You'll need both legs sorted though to complete this quest. 

There are two easy(ish) options to get the Ballistic Fiber you need here. Tracking down a travelling merchant who sells a 25 Ballistic Fibre shipment, or checking a couple of locations that have a few rolls of Military Duct Tape lying around. The merchant is easiest, so let's do that first...

Lucas Miller is a travelling merchant selling a shipment of Ballistic Fibre. He moves around the north east part the map between Greentop Nursery, Malden, Tenpines Bluff and Covenant, and also sometimes appears at a market stall in Bunker Hill. (I found him at Greentop Nursery.) If you find him you can simply buy 25 pieces of Ballistic Fiber, which is more than enough to finish the mission. 

Fallout 4 crucible lucas miller route and location

(Image credit: Bethesda)

However, if for any reason you can't find Miller you can also find some Military Grade Duct Tape in Gunner Place and Vault 75, which is found under Malden Middle School.

fallout 4 Gunner Place and Vault 75

(Image credit: Bethesda)

For Gunner Place you can find two pieces of Military Grade Duct Tape inside one of the side cubicles in the large round room once inside. Just look for a medical gurney by some desks: 

fallout 4 Gunner Place Military Grade Duct Tape

(Image credit: Bethesda)

As for Vault 75, look for the destroyed wall of the Malden Middle School to get into the basement and then use the elevator to go down a level. When you leave the lift, look on the left as you move forward for a table with some Military Grade Duct Tape on it. There's a second roll of tape in the room just next to the table. 

fallout 4 crucible

(Image credit: Bethesda)

That should get you four pieces of tape between these two locations which, with the three you found buried, will give you 14 pieces of Ballistic Fiber. You need six per leg so that's more than enough. 

The rest of what you need should be much easier to source, and the chances are you'll have more than enough at any settlement you've been rebuilding. But, if you don't want to go back and get that, or want to grab some while you're out, let's quickly run through it all:

Where to find Adhesive in Fallout 4

It's relatively easy to find adhesive in Fallout 4. Just look out for any of these junk items, which will break down into adhesive when you use it for crafting.  

  • Wonderglue
  • Economy wonderglue
  • Sealed wonderglue
  • Duct tape
  • Pack of duct tape
  • Military grade duct tape

Where to find Asbestos in Fallout 4

Asbestos is actually pretty easy to find in Fallout 4, it's just not obvious what actually has this resource in it. Look out for any of these which will breakdown to give you Asbestos when you need it. 

  • Pack of cigarettes / Cigarette carton
  • Coffee pot / Luxobrew coffee pot
  • Extinguisher
  • Oven mitt
  • Biometric scanner
  • Chalk
  • Rat poison
  • Teapot

Where to find Rubber in Fallout 4

Chance are you'll have plenty of Rubber from scrapping tyres and the like at settlements. But, if you want to grab some without heading back, look for these items: 

  • Kickball
  • Plunger
  • Toy alien
  • Basketball
  • Bonesaw
  • Extinguisher
  • Saw
  • Spatula

How to complete the Crucible in Fallout 4

fallout 4 crucible

(Image credit: Bethesda)

Once you've got all the things you need (Ballistic Fiber), simply head back to Sangus Iron works and mod the power armor legs to be flame resistant. Then you can simply walk across the molten metal and take the Heavy Incinerator. Done.

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Leon Hurley
Managing editor for guides

I'm GamesRadar's Managing Editor for guides, which means I run GamesRadar's guides and tips content. I also write reviews, previews and features, largely about horror, action adventure, FPS and open world games. I previously worked on Kotaku, and the Official PlayStation Magazine and website.