Minecraft wiki entry for Shulker, associated text: Shulkers occasionally open their shell for 1–3 seconds to peer outside. When a target comes within about 16 blocks, it opens fully and shoots guided projectiles that follow the player, called shulker bullets, moving only along the X, Y, or Z axes and leaving trails of white particles. The projectiles can be destroyed by attacking them or blocked with a shield. If the projectile hits an entity, it does 4 of damage and inflicts the Levitation status effect for 10 seconds. (Levitation has no effect underwater, or while riding the mobs.) The shulker continues firing every 1–5.5 seconds while the target remains in range. If the shulker's target dies with projectiles still in flight, they fall to the ground.