Minecraft wiki entry for Armor, associated text: Certain mobs can spawn equipped with random armor pieces. Some mobs also spawn with the ability to pick up the armor on the ground and equip them. The probability of mobs spawning equipped with armor, whether the armor is enchanted, the level of the enchantment of the armor, and how many pieces of armor a mob spawns with depends on the difficulty; if a mob spawns with armor, the tier of armor (leather, gold, etc.) has a fixed probability: