Amulet of Mage Armor

Once per day, the wearer may use the amulet to cast the Mage Armor spell as an action.

When activated, a protective magical force surrounds the wearer until the spell ends. The target’s base AC becomes 13 + its Dexterity modifier. The amulet will not activate if it's owner is already wearing Armor. The spell ends if the wearer removes the amulet, dons armor or if they dismiss the spell as an action.

If your DM allows it, it may be possible to upgrde the Amulet's number of spell charges and uses per day. subject to your world's rules of magic.

Notes: unarmored owner.