Minecraft wiki entry for End_survival, associated text: Second, once the buildings and infrastructure are in place, the player can transport animals and villagers to the island. Chickens can be brought in the form of eggs and hatched anywhere in the world, but other mobs will need to be pushed or lured through the End portal. The player is advised to block off the return portal, as this will teleport any mobs who fall through it to the player's spawning spot in the Overworld. Provided that the player has brought villagers through the gateway, it is possible to build iron farms in the End, giving the player infinite iron to make weapons and armor to fight the Dragon with once the initial farm is set up on an outer island.