From Turf Battles Wiki

These items are used for defense. Always remember to check the stat requirements of armors you have equipped to your character so that losing an accessory or other item that enhances your stats does not negate that armor. If you have recently died and lost a piece of your equipment or changed a piece of equipment and your character is taking more damage, make sure you are still stated correctly to use your equipped armors. These items can provide additional stats in some cases for the base stats of STR, DEX and VIG. Classes have specific options for their armor sets and additional options cannot be added besides the options specified for them. For example, Red Mage armor can only have Strength, Magic Recovery, Defense and Magic Defense and other options cannot be added. Other items like Shields and Protectors have a wider variety of options and attack more like Weapons while not providing attack power.