The demon lord cannot stand anyone calling him stupid. When the Almighty Book states that demon lord Zeta is an idiot who will bring the end to his world, he lets lose the flames on the book. But instead of the book, it is his world and his body that turn into ashes.
To gain his body back, he binds the souls of his dead citizens to form an army. Your troops are no longer bound to the squares of the battlefield. You may move as far and as many times as you need in your turn. And as the demon lord, you can call forth buildings to stop your enemies or bombard them.
You have the Almighty Book in your hand, use the information, create your army and fight your war.