You finally made it to Grymforge. You’ve dodged the traps, dealt with the Duergar, and now you’re staring at this massive, ancient hunk of machinery. But here is the thing: you only get two shots at this. There are only two chunks of Mithral Ore in the entire game, which means those six shiny adamantine forge bg3 moulds you’ve been collecting aren't all getting used.
Most players mess this up. They see "Adamantine Longsword" and think it sounds legendary. Honestly? It's kind of a trap.
Getting the right gear here can carry you through the end of Act 2, but pick the wrong mould and you’ve basically wasted the rarest resource in the Underdark. Let’s break down where these things are hidden and which ones actually deserve a spot in your inventory.
The "Big Six" and where to find them
You can't just buy these. You have to scavenge them from the ruins of Grymforge, and Larian didn't exactly make it easy. They’re scattered across high ledges, tucked away on skeletons, and sitting on random worktables.
1. The Splint Mould (Heavy Armor)
This is the holy grail. You'll find it north of the Ancient Forge waypoint. If you’re heading up the stairs, look on a rocky ledge to your left. It’s just sitting there, waiting for someone to give it to a Paladin or Fighter. This creates the Adamantine Splint Armour, which has an AC of 18 and makes you immune to critical hits. That’s huge.
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2. The Scale Mail Mould (Medium Armor)
Located right near the Ancient Forge waypoint, south of where the Animated Armours are hanging out. It’s lying on the ground near some steps. If you have a Cleric or a Ranger, this is usually your second-best pick. 16 AC plus your Dexterity bonus (up to +2) means it’s just as good as the heavy stuff but for the more nimble crowd.
3. The Shield Mould
This one is tucked away in the Dormitory area. You have to go to the upper levels east of the main docks. Look for a skeleton at the top of some rubble. The Adamantine Shield is arguably the best item for anyone who can’t wear the heavy armor but still wants that sweet "no critical hits" buff.
4. The Longsword Mould
Found on the hanging metal catwalks. You’ll likely see this while you’re messsing around with the levers to move the platforms. It’s sitting on the central bridge section. It sounds cool, but unless you really love the "Diamondsbane" perk (guaranteed crits against objects), it’s usually not worth the ore.
5. The Scimitar Mould
You’ll find this on a skeleton near the two levers that control the moving platforms. It’s right near the ruined stairwell overlooking the area where Nere is trapped.
6. The Mace Mould
The easiest one to find. It’s literally sitting on a table right next to the Ancient Forge waypoint. If you missed this, you might need to check your eyesight.
The trap of adamantine weapons
Look, I get it. A glowing blue sword feels like the right move for a fantasy RPG. But in Baldur’s Gate 3, the adamantine forge bg3 moulds for weapons are objectively worse than the armor.
Why? Because of how the math works.
The weapons have a feature called Diamondsbane. This ensures that any hit against an object is a critical hit. This is great for smashing down doors or chests without using lockpicks. But how often are you fighting doors compared to, say, a literal god of death or a pack of gnolls? Against enemies, the weapons are just standard +1 gear. You will find better weapons at the start of Act 2. You will not find better armor for a very long time.
Why armor is the real winner
The Splint and Scale Mail versions of the Adamantine gear have three massive benefits that keep them relevant until the very end of the game:
- Crit Immunity: In BG3, a lucky crit from an enemy can end your run. This armor makes that impossible.
- Reeling: When an enemy hits you, they get a -1 penalty to attack rolls for two or three turns. They essentially get "dizzy" for trying to hurt you.
- Damage Reduction: You take 1 or 2 less damage from every single source. It doesn't sound like much, but when you're being peppered by arrows, it adds up fast.
If you’re playing on Honor Mode, crit immunity isn't just a "nice to have"—it’s a life insurance policy.
How to actually use the forge without dying
Finding the adamantine forge bg3 moulds is only half the battle. Once you have them, you have to actually use the thing.
First, walk to the center. Put your chosen mould into the Mould Chamber and your Mithral Ore into the Crucible. Pull the Forge Lever. The whole platform will drop down into the lava pit. This is where things get messy.
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Turning the Lava Valve spawns Grym, a massive mechanical guardian who is basically immune to everything unless he’s "Superheated" by the lava.
Pro tip: Position a character by the central lever. If you can lure Grym onto the middle platform (the Crucible) while he’s standing in lava, you can pull the lever to smash him with the giant hammer. It does massive bludgeoning damage. Two or three hits from the hammer, and the boss is toast. Just make sure your own party members aren't standing under the hammer, or you’ll be the one getting forged into a pancake.
The ultimate Act 1 strategy
If you want the most "meta" outcome for your party, here is what most experts do. They grab the Splint Mould for their tank (Lae'zel or a Paladin Tav) and the Shield Mould for their support (Shadowheart).
The shield is sneaky good because it applies "Reeling" to enemies when they miss you. It turns your high AC into a weapon.
If you don't have a shield user, go for two sets of armor. One Heavy, one Medium. This setup provides the most longevity. You’ll find yourself still wearing this gear when you’re walking into the final battles of Act 2, whereas that Adamantine Longsword would have been sitting in your camp chest for twenty hours by then.
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Once you’ve used your two Mithral Ores, the forge is done. You can keep the remaining adamantine forge bg3 moulds as souvenirs, or just sell them to a merchant for a few extra gold pieces. They have no use once the ore is gone.
Make sure you've picked up both pieces of ore before leaving the area. One is across the lava to the left of the stairs leading down to the forge, guarded by some pesky Magma Mephits. The other is southwest of the Ancient Forge waypoint, tucked behind some rocks near a lava pool. Grab them both, pick your two favorite moulds, and go kill that golem.