Minecraft wiki entry for The_End, associated text: The player can activate the portal by placing 12 eyes of ender into the 12 end portal frames. Each frame block has a 10% chance of generating with an eye in it already, meaning the player may not necessarily use 12 eyes to activate it. Once all the eyes of ender are placed, the portal activates and emits a loud noise. As soon as it is activated, the portal destroys all blocks in the central 3×3 square, including bedrock or another portal frame, and replaces them with the end portal blocks that can teleport an entity into the end dimension. Upon jumping into the portal, the player immediately arrives in the End (x: 100, z: 0), along with any prior entities that may have teleported.