Armor

 Not to be confused with the Power Armor or Octoling Armor clothing.

Armor or armour (officially known as Aragonite Armor) is a protective collectible in Splatoon's Hero Mode. The armor is automatically worn by Agent 3 (the player) when picked up.

Description
Armor comes in a small briefcase-like collectible on singleplayer Hero Mode missions.

Agent 3 can hold up to three pieces of armor. Though the armor collectible is the same, Agent 3's appearance changes depending on how much armor they are wearing.

Use
The armor prevents enemy Octarian attacks from splatting Agent 3. If Agent 3 takes enough damage that would otherwise splat them, an armor piece breaks instead.

Having armor on at the end of a Hero Mode mission awards a bonus 10 Power Eggs.