Armor of Invulnerability

Source: Dungeon Master's Guide

Armor (plate), legendary (requires attunement)

You have resistance to nonmagical damage while you wear this armor. Additionally, you can use an action to make yourself immune to nonmagical damage for 10 minute or until you are no longer wearing the armor. Once this special action is used, it can't be used again until the next dawn.

armorattuneddmglegendary