Minecraft wiki entry for Shelters, associated text: Sometimes called a panic room, a Bunker is a small room made of strong materials (obsidian for example) with an iron door with the open/close system inside the room. This room must have a bed, a crafting table, a furnace and also a chest with the basic materials (food, tools, armor and weapons are a must). It also has to have a high interior luminosity to avoid monsters spawning inside. It should also be only two blocks tall so Endermen can't teleport inside.