Dreadnought Armor (5e Equipment)
From D&D Wiki
Armor (plate), very rare
The dreadnought armor was designed by the dwarves after they discovered that adamantine could be compressed. Despite being designed to maximize mobility, even going so far as to reduce its weight using runes, only the strongest could use it. While you're wearing this armor, any critical hit against you becomes a normal hit and you have a +2 bonus to your AC.
Heavyweight. If you have don't have 19 Strength, while wearing this armor, your movement speed is halved.
Clunky. It takes 30 minutes to don this armor, and 10 minutes to doff this armor.