Celestial sphere

Celestial Spheres
All Wildspace is bounded by the crystal shells of the Celestial Spheres. Inside the Celestial Spheres is the vacuum of wildspace, the planets, and stars. Outside the Celestial Spheres in the rainbow fog of phlogiston and more Celestial Spheres.

The size of a Celestial Spheres is determined by the size of the planetary system inside. Usually a sphere has a radius at least twice as big as the orbital radius of the outermost celestial body in the system.

Because of their great size, the outside of a Celestial Spheres appears perfectly flat. The curvature in completely undetectable to anyone who is close enough to see the Celestial Spheres through the obscuring phlogiston.

The spheres consist of an unbreakable, dark, glass-like material of unknown origin.

The Celestial Spheres are normally solid. They have no gravity along either their interior or exterior sides. No magic in known that can damage or alter the surface of a shell, except for those spells which cause portals to open. Even this, however, is believed to be nothing more that an artificial triggering of a natural phenomenon, since portals also occur naturally.

portals
Portals in the Crystal shell look like the black depths of an ocean. the Surface of a portal have the gentle undulations of a reflecting pool. Anything the crosses the boundary causes the surface to fracture and fold in on it self, like an object braking through a like of ice on a pond. ((Lost in space movie time bubble effect)) Someone can not use this effect to break off a piece as any force on the portal with cause one to move into or out of it. Though the surface is transparent and one can see objects that have already entered one can see anything on the other side. Things completely enter one side of the portal before they start exiting the other side. Magic that relies on other planes is notoriously unreliable when cast in close proximity to a crystal shell.

Portals in the Crystal Shells are merely simple doorways allowing passage from one side of the shell to the other. They are not gates and they do not allow transit between the planes.