You’ve spent hours crawling through the Underdark. You’ve dodged traps, dealt with a bunch of annoying Duergar, and finally, you see it—the massive, soot-stained platform of the Baldur's Gate 3 Adamantine Forge. It’s one of the most iconic "eureka" moments in Act 1. But honestly? It’s also where a lot of players make a mistake that haunts them for the next thirty hours of gameplay.
Finding the place is only half the battle. You’re standing there with two precious pieces of Mithral Ore, staring at six different moulds, wondering if you should get that shiny longsword or go for the heavy plate.
Don't panic. We’re going to walk through how to actually use this thing without blowing up your party, which items actually matter, and how to deal with Grym—the giant mechanical jerk guarding the place—without losing your mind.
How the Baldur's Gate 3 Adamantine Forge Actually Works
Basically, the forge is a giant 3D printer from the ancient Sharran era. You need three things to make it go: a mould, some ore, and a whole lot of lava.
First off, you have to find the Mithral Ore. There are only two veins in the entire game. One is tucked away to the left of the path as you head down to the forge (watch out for the Magma Mephits that jump you). The other is further back, guarded by some animated armors. You have to literally "kill" the rock with bludgeoning damage to get the ore out.
Once you have the ore, you head to the center of the platform.
- Drop the Mould: Interact with the Mould Chamber (it looks like a metal arm sticking out) and put your chosen mould in.
- Insert the Ore: Click the big round Crucible in the center of the forge and slot in your Mithral.
- Hammer Time: Pull the Forge Lever on the side. The whole platform will descend into the depths.
- The Lava Valve: Once you’re down there, turn the valve. This floods the floor with lava.
Pro tip: Make sure your characters are standing on the raised circular bits or the walkway. If they’re standing in the channels when you turn that valve, they’re going to have a very bad, very melty day.
The Grym Problem (And How to Cheese Him)
The second that lava starts flowing, Grym shows up. He’s a massive Eternal Protector with about 300 HP (on Balanced) and a serious attitude problem.
Here is the thing: Grym is basically invincible unless he’s "Superheated." He only gets that status by standing in the lava. If the lava goes away, he becomes immune to almost everything. You have to keep the floor flooded to even touch him.
Most people try to fight him "the right way" by luring him under the massive central hammer and pulling the lever. It deals massive bludgeoning damage and knocks him prone. It’s satisfying. It’s also kinda finicky because you have to time his "Threat" mechanic—he always moves toward the last person who hit him.
If you want the "Chad" way to do it? Use a Druid. Turn into an Owlbear. Jump from the high walkway above the forge directly onto his head. Because of the way Baldur's Gate 3 calculates crushing damage based on weight and distance, you can actually one-shot him. It’s hilarious and saves a lot of healing potions.
Which Adamantine Items are Actually Worth It?
This is where the real debate happens. You only get two items. Choose poorly, and you’ve wasted a legendary resource on a weapon you’ll replace in five hours.
The "Absolute Must-Haves"
1. Adamantine Splint Armour (Heavy)
This is the king of the forge. It gives you an AC of 18, reduces all incoming damage by 2, and—this is the big one—makes the wearer immune to critical hits. In a game where a random crit from a boss can end your Honor Mode run, this is gold. It also sends attackers "Reeling," giving them a penalty to hit you.
2. Adamantine Shield
If you don't have two heavy armor users, get the shield. Like the armor, it makes you immune to crits. It also lets you use a "Shield Bash" reaction to knock enemies prone. It is arguably the best shield you’ll find until deep into Act 2 or even Act 3.
The "Maybe" Category
Adamantine Scale Mail (Medium)
It’s basically the medium version of the splint. It has 16 AC and reduces damage by 1. It’s great for Shadowheart or a Ranger, but there are some really good medium armors in the early parts of Act 2 (like the Yuan-Ti Scale Mail) that might make this feel redundant sooner than the heavy version.
Why You Should Probably Skip the Weapons
Look, the Adamantine Longsword, Scimitar, and Mace look cool. They have a "Diamondsbane" feature that makes every hit on an object a critical hit. Great for breaking down doors!
But for actual combat? They’re just +1 weapons. By the time you reach the Baldur's Gate 3 Adamantine Forge, you probably already have things like the Blood of Lathander or various +1/+2 weapons from the Crèche or the goblin camp. Don't waste your Mithral on a sword when the armor can keep you alive through the entire game.
Common Bugs and How to Fix Them
Sometimes the forge gets "stuck." You’ll try to pull the lever and it says "It won't budge." Usually, this happens because there’s still a mould in the chamber or the platform hasn't reset.
If the Mould Ejection Lever isn't working, try hitting the "Reset" button (the tiny button near the main lever). If all else fails, save your game and reload. Baldur's Gate 3 is a masterpiece, but the forge is notoriously one of its glitchiest areas.
Your Next Steps
Stop staring at the moulds and make a decision. If you have Lae'zel or a Paladin Tav, craft the Adamantine Splint Armour first. It is a game-changer. For your second item, grab the Shield or a second set of armor.
Once you’ve got your gear, don't forget to loot Grym’s corpse for the Grymskull Helm. It gives you even more crit immunity and Hunter's Mark. With the splint, the shield, and the helm, half your party will be walking around practically immune to the luck of the dice. Now, get out of the lava and head toward Act 2.
🔗 Read more: Stardew Valley Void Salmon: How to Finally Catch One and Why They’re Actually Useful
To finish your Underdark run properly, head back to the Myconid Colony to turn in your quests before you take the elevator or the mountain pass—you'll want those extra rewards before the difficulty spikes in the Shadow-Cursed Lands.