The top of each pillar explodes, destroying any player-placed blocks.
When it is re-summoned, the four end crystals point to the tops of each pillar setting off a series of explosions that resets the obsidian pillars, iron bars, and end crystals. Players can re-summon the dragon by placing four end crystals on the edges of the exit portal, one on each side. This image shows how the player can arrange end crystals to respawn the ender dragon. The ender dragon spawns 20 game ticks (1 second) after an entity first arrives in the End, along with the bedrock frame for the exit portal.
