Nyr-metal Armor (5e Equipment)
From D&D Wiki
Armor (Medium or heavy, but not hide), very rare
This pinkish metal is impressively lightweight, being even lighter than mithral armor, but isn't nearly as flexible.
When wearing this armor, consider it one category of armor lighter, and any strength requirements are reduced by 3.
the weight of armor is reduced, in the case of all armor 40 lb. or heavier by two-thirds, for the rest of medium armor one half - for the sake of calculating lifting/carrying limits.