Wily Citadel 4 is the World Boss level in World 3, The Megaverse. It is the last level before facing off against World 3's World Boss. While it does not actually contain a World Boss-class boss battle, the level is labeled as a World Boss stage is it is where the player will face off against Dr. Wily in person for the first time. After all 8 Masters have been defeated, a path to the final checkpoint will open up. Inside the player will enter one last teleporter, which will transport them to the boss room.