Minecraft wiki entry for Defeating_the_ender_dragon, associated text: Destroying the end crystals is a key part of the battle, because they heal the dragon. With all of the crystals active, the dragon recovers faster than you could ever hope to damage it under normal conditions. It is possible to defeat the dragon while some crystals remain, provided the dragon spends enough time away from them, but it is best to destroy all of them. One end crystal sits atop each obsidian pillar. There are usually eight to ten towers of different heights arranged in a circle around the empty exit portal. The crystals on the tallest towers may be difficult to see, but the healing beam they emit when the dragon is nearby reveals their locations. Try to destroy a crystal while it is healing the dragon because the dragon takes 10 damage if you do this.