In the first act of Baldur’s Gate 3, you can traverse not only the wilderness of Faerun, but the recesses of the Underdark. Within the underground chasm rests an Adamantine Forge that requires both a mold and a supply of Mithril Ore to create both weapons and armor.
Finding this Mithril Ore can be somewhat challenging, however. I didn’t find any my first time around, but upon reloading a save, and doing a fair amount of exploration, I found both mineral deposits. That’s right — there are only two sources of Mithril Ore in Baldur’s Gate 3, and they can both be found in the Grymforge area of the Underdark, just a hop and a skip away from the forge itself.
Where to find Mithril Ore in Baldur’s Gate 3?
To find both Mithril Ore locations, use the Underdark — Ancient Forge waypoint as a milestone. From there, go south until you reach a battle with a set of Animated Armour (unless you’ve already by some chance beaten them). If you haven’t, there are only four enemies so make quick work of them.
Take a left at the checkpoint with the netting and follow the path around and below to the right. Jump across the river of lava and you should see the Mithril Vein, which can be broken into Mithril Ore by using bludgeoning damage (or by shooting it with arrows).
Return to the Ancient Forge waypoint and head straight southeast, toward the forge itself. To reach it, you’ll have to descend a very old, very fragile set of stairs. But, if you glance to the left whilst on this staircase, you’ll see the gigantic Mithril Vein sitting a short distance away. To claim your prize, however, you’ll have to fend off a horde of Magma Mephits, but they are hardly anything to be concerned about.
Take care of your newfound winged “friends” and proceed northeast to reach the Mithril Vein. In the same way you handled the last one, use bludgeoning damage or arrows to break it apart and claim the Mithril Ore inside. It would seem that is the last possible Mithril Ore in Baldur’s Gate 3. That makes a ton of sense given the game eventually prevents you from returning to the Adamantine Forge entirely.