Realmspace

Realmspace is about 6,400 million miles in diameter. The shell, whether viewed from the inside or outside, looks like a perfectly flat, solid wall. The surface, somewhat bumpy and cold to the touch, is completely immune to nearly every known damage, attack or spell. Nothing known in the universe can begin to tear or crack it. This indestructibility is a blessing for the inhabitants within the sphere. If the crystal shell were ever to be breached, the phlogiston outside would doom the planets inside. The phlogiston would cause worldwide atmospheric burning, and the sun would ignite into a fireball powerful enough to disintegrate every planet in the sphere.