Adamantine

An ultra-hard alloy of adamant and electrum. Adamantine is black with a green tinge that sharpens to purple-white under light from most magical sources. While you’re wearing the armor, any critical hit against you becomes a normal hit. In addition, when you are subjected to a magical effect that allows you to make a Strength or Constitution saving throw to take only half damage, you instead take no damage if you succeed on the saving throw.

Shields made of adamantium have a +1 bonus to AC.

Equipment made of adamantine can’t be destroyed, damaged or suffer from wear.