Where to Find Infernal Iron in the Underdark (BG3 Guide)

Where to Find Infernal Iron in the Underdark (BG3 Guide)

Looking for where to find Infernal Iron in the Underdark in Baldur’s Gate 3? Then you're probably dealing with Karlach's broken engine. Don't worry — I've been there, and I'll show you exactly where to grab this stuff without getting yourself killed.

This isn't the only Infernal Iron in the game, but it's the easiest one to miss. It's sitting in Grymforge, the big dwarven forge area with lava pits and a tough boss fight later. The good news? You won't need to fight Grym to get this piece.

Where to Find Infernal Iron in the Underdark (Step-By-Step)

Here's the exact route. Follow it and you'll be in and out before the Duergar even notice you.

1. Enter the Underdark.
Use the well in the Blighted Village, or take the lift in the Goblin Camp near Priestess Gut's room. Both routes work, so pick whichever one fits your playthrough.

2. Head to the Grymforge.
Follow the main path to the beach area where a group of Duergar are hanging out by a boat. Talk them into taking you across, or kill them and take the boat yourself. Either way, you'll reach Grymforge.

3. Walk to the central forge building.
Once you arrive, look for the ancient stone structure with Duergar working around it. Head toward the middle, where you'll see a big forge with an anvil and broken equipment scattered around.

4. Go up the wooden stairs on the left side.
Inside the forge building, look left. You'll see a short set of wooden stairs leading to a small platform. Once you're at the top, look right.

5. Open the wooden chest behind the crates.
There's a small brown chest tucked behind a couple of broken crates and a barrel. Open it, grab the Infernal Iron, and get ready to head back.

It's really easy to walk right past this chest. You're probably focused on the Duergar leader, the grymforge quests, or the ancient forge mechanics. Trust me — that little chest is the one you want.

How To Use Infernal Iron With Dammon To Fix Karlach

Alright, you've got the Infernal Iron. Now you need Dammon.

Dammon is a tiefling blacksmith who first shows up in the Emerald Grove. He stands near his anvil in the corner of the Druid Grove, right next to the tiefling refugees. If you've already handled the goblin camp rescue and Halsin isn't an issue, Dammon might have moved on to the Last Light Inn in Act 2.

Here's how to fix Karlach:

1. Talk to Dammon.
Pick the dialogue option about Karlach. If she's in your party, she'll jump in and explain what's going on.

2. Give him the Infernal Iron.
As long as you have at least one piece in your inventory, Dammon will take it and start working on Karlach's chest.

3. Watch the repair cutscene.
Dammon does his thing, Karlach feels better, and her personal quest moves forward. You'll also get some new dialogue options with her.

4. Keep any extra Infernal Iron.
If you've got more than one piece, don't spend it yet. In Act 2, Dammon can craft Flawed Helldusk armor and other infernal equipment with it. But Karlach's heart repair should always come first.

Common Mistakes To Avoid When Hunting For Infernal Iron

I've seen players mess this up. Don't be that person.

1. Selling Infernal Iron to a merchant.
It looks like junk metal, but it's not. If you sell it, you might not get it back easily. Always keep at least one piece in your inventory or traveler's chest.

2. Waiting until after the Grove is gone.
If you don't give Dammon the metal before the goblin raid on the Druid Grove, you might lose him. If Dammon dies, you lose your chance to fix Karlach in Act 1. You can still find him in Act 2 if he survives, but if he's dead, that part of her quest is locked.

3. Rushing through the Underdark on the main path only.
The Infernal Iron chest is off the beaten path. If you skip the side room, you'll miss it completely. Follow the stairs-to-the-left step above and don't skip it.

4. Using Infernal Iron for crafting too early.
Yes, Dammon can eventually craft strong gear from Infernal Iron. But fix Karlach first. Her heart repair is time-sensitive and directly tied to her romance and questline. You can't get another chance if you waste your only piece.

5. Forgetting to loot the chest after a fight.
The chest isn't trapped or guarded, but if you trigger a fight with nearby Duergar, it's easy to forget. Clear the area first, then do a slow sweep of the forge building. That's how I found it the first time.

FAQ: Infernal Iron, Underdark, and Karlach

Can you find more than one Infernal Iron in the Underdark?
The guaranteed piece is in Grymforge, right where I showed you. There are other Infernal Iron locations in the game too, like the Blighted Village blacksmith area and the Goblin Camp's worg pen. But if you're specifically hunting in the Underdark, Grymforge is the place.

Do you need the Underdark piece of Infernal Iron to fix Karlach?
No, you just need any one piece of Infernal Iron from anywhere. If you already found one in the Blighted Village or Goblin Camp, you can skip the Underdark piece. But grabbing this one gives you a spare for crafting later, so it's worth the detour.

What happens if Dammon dies before I give him the Infernal Iron?
That's a big problem. Dammon is the only reliable blacksmith who can repair Karlach's engine in Act 1, and he's essential for her questline in Act 2. Give him the metal as soon as you recruit Karlach and get your first piece.

Is there any other use for Infernal Iron?
Yes. In Act 2, Dammon can craft Flawed Helldusk gear from Infernal Iron, including armor, gloves, and boots. These are genuinely strong pieces for a fire-based build. But always save at least one piece for Karlach first. The rest is bonus.

Now you know exactly where to find Infernal Iron in the Underdark and how to use it. Grab that chest in Grymforge, haul it back to Dammon, and get Karlach to stop overheating. Then worry about the next threat in Baldur's Gate 3 — because there's always one waiting around the corner.