In this chapter, we learn that the demon king is pulling at the ceiling and floor with his ether gear. He's like a black hole. The ether gear is a critical point in the battle plan, and they'll use their own gear to make up for the loss of the main cannon. They can't use the blue garden because it's dormant, but they can use the ether gear to break through to the other side of the wall. They're going to use their gear to do the work.