Minecraft wiki entry for Defeating_the_wither, associated text: A more advanced tactic that is very rewarding would be to construct a cobblestone generator-powered grid above the player, spawn the Wither about 15 blocks away, and stand under the grid. The wither will fly toward the player, but it would be kept at the edge of the grid, constantly being pushed back by the cobblestone which is generating faster than what the wither can break. This allows the player to stand still and shoot the wither without retaliation, until the Wither is at half health, where it will fly toward the player through the grid, allowing the player to easily kill the Wither with a sword. In addition to that, the player can rig dispensers about 15 blocks away to periodically shoot splash potions of health, which heal the player and damage the wither.