Minecraft wiki entry for Defeating_an_End_city, associated text: Potions are highly recommended to have when you explore a city, to enhance your performance. Strength potions, invisibility potions, and swiftness potions can be extremely useful. When you use an invisibility potion, mobs can still see you if you are wearing your armor. To stay safe, take off all of your armor before drinking it, and put it back on at least 30 seconds before the effect expires.