Adamantine Splint Armour is a Rare Heavy Armour found in Baldur's Gate 3.
Where To Find The Adamantine Shield In Baldur's Gate 3
The Adamantine Splint Armour is one of several items that can be forged at the Adamantine Forge, located in the Underdark, and is tied to the quest "The Adamantine Forge". To obtain the Adamantine Shield from the forge, you will first need to gather the Shield Mould, 
Mithral Ore and defeat Grym. Once all of these conditions have been met, you can then forge the Adamantine Splint Armour and equip it for use.
The Adamantine Forge Location
Below is the location where you can forge the Adamantine Shield (Grymforge region).
