Crystal spheres are one of the unusual features of Spelljammer that set the game apart from other fantasy space roleplaying games. Some people really like them – other people dislike them and tweak the game to remove them. I would like to tell you why I think crystal spheres are a really useful part of the SJ Universe, but first, here is a reprint of the crystal sphere article I wrote for Spelljammer Wiki.
A crystal sphere, also known as a crystal shell, is an object of great size that surrounds an entire planetary system and forms a boundary that separates wildspace from the phlogiston.
The size of crystal spheres is related to the size of the planetary system within them. As the name ‘crystal sphere’ implies, the objects are spherical.
Although they are solid, crystal spheres have no gravity and no atmosphere. The material crystal spheres are made of is a unbreakable dark ceramic material. No magic is powerful enough to damage crystal spheres.
Travel through a crystal sphere
Only a few methods are known to allow travel from one side of a crystal sphere to the other side.
Teleport or Dimension Door spells
These spells (or magical devices that duplicate them) allow spellcasters to jump from one side of the sphere to the other without physically crossing the sphere.
Phase Door spell
This spell (or a magical item that duplicates it) makes part of the crystal sphere immaterial and allows a spelljamming ship to pass through.
Naturally occurring portals
Most crystal spheres have natural portals that pierce the shell at various locations. These portals usually and vanish at random times and are located in random places. Looking for these portals can take a long time.
In some crystal spheres, stars are located on the inside of the crystal shell. A few of these stars are themselves also natural portals through the crystal sphere. A spelljamming ship diving into the heart of the star would pass through the shell and appear in the phlogiston. However, a high number of stars are portals to the Plane of Radiance or the Plane of Fire. Flying a ship into one of those stars would be fatal.
The Spelljammer and creatures like space dragons
The legendary ship, called The Spelljammer, and some large space creatures, like space dragons, seem to have an innate ability to create portals similar to the natural portals. These portals close slowly over time, so ships can sometimes use them.
The Create Portal spell
This spell duplicates the natural ability of The Spelljammer and space dragons, but the portals created by this spell have a much shorter duration. Portals created via this spell last no longer than 120 minutes.
Individual crystal spheres
Size of individual crystal spheres
The size of crystal spheres is usually determined by the size of the planetary system within them. Each sphere usually is usually twice the diameter as the outermost planet within the crystal sphere, but spheres can be larger than this. There are often astronomical objects that defy this ‘double diameter’ rule and orbit outside the outermost planet. Sages who support the ‘double diameter’ rule usually argue that these celestial bodies are additional astronomicals rather than true planets.
It is possible for a crystal sphere to contain another crystal sphere, or a series of smaller and smaller crystal spheres.
There are six main theories about the origin of the crystal spheres.
The gods created the shells and the flow
The gods created the spheres and the Phlogiston in order to divide up the universe. The gods split the universe into chaos (the flow and order (the spheres). They then divided up the individual spheres among themselves in order to test law against chaos and good against evil.
The gods have their own gods
These gods-of-gods created the universe, and then placed the gods into the universe. This theory gained more popularity in Realmspace in recent times.
The Phlogiston is a naturally occurring object
The Phlogiston was there before the gods. The gods built the crystal spheres to settle and domesticate the flow. The spheres are like cities built along a stream and eventually they will grow and join together. When this happens the Phlogiston will cease to exist.
The gods fear the flow
The gods fear the Phlogiston and built the spheres to keep it out.
The gods fear men and other sentient beings
The gods fear humans and other sentient creatures and built the crystal spheres to keep them in.
The Phlogiston and the shells are naturally occurring
Someone or something created the entire universe and the gods moved in and took over. There is a secondary implication, that the gods have lied about creating the universe to deceive mortals.
That is what the canon of Spelljammer tells us about the facts and beliefs about crystal spheres that are held within spacefaring communities. In Part 2, I will tell you How Crystal Spheres can Improve Your Game.