Adamantine Armor

DMG'24

Armor (Any Medium or Heavy, Except Hide Armor), Uncommon

Cost: 400 gp

Base Items: Breastplate, Chain Mail, Chain Shirt, Half Plate Armor, Plate Armor, Ring Mail, Scale Mail, Spiked Armor, Splint Armor, Pavise, Shield

This suit of armor is reinforced with adamantine, one of the hardest substances in existence. While you're wearing it, any Critical Hit against you becomes a normal hit.