Spelljammer-Adventures In Realm Space
Outside and between the crystal spheres is a turbulent, rainbow ocean of flammable ether called the phlogiston. The phlogiston is a multicolored sea upon which float the various systems within their crystal shells. The term phlogiston is applied equally to both the multicolored medium and to the entire region surrounding the crystal spheres.
Phlogiston has varying thicknesses in space and forms dense rivers between planet-sized objects (such as the spheres themselves). Voyagers moving along these paths of concentrated phlogiston discover that the greater the density of the flow, the faster a ship can move. A ship can speed up and slow down by penetrating deeper into or raising itself out of these phlogiston rivers. Steller distances can be covered quickly in such areas. Further, the speed of the ship is at least partially dependent on the surface area it presents to the flow, so many ships carry sails to increase their speed in the interstellar ocean.
Gravity works in phlogiston the same way it does in wildspace. Down is directed toward the major axis of the ship.
Phlogiston is none of the recognized four elemental matters. It is neither air nor earth, fire nor water. It cannot be reproduced or brought inside the bounds of a crystal sphere. If an attempt is made, whether by physical or magical containment, the phlogiston inexplicably dissipates, leaving no trace. Phlogiston simply cannot exist within wildspace or on the surface of a planet.
Finally, phlogiston is dangerously flammable, much like oil-soaked cotton, which poses its own problems. Any flame exposed to phlogiston causes the surrounding area (including the phlogiston-laden air envelope of the ship) to burst into flame. This flame expands immediately to three times its normal diameter and inflicts three times its normal damage. For this reason, fireballs, bombards, arquebuses, and any other weapons which rely on a spark or flame are not used in the phlogiston.
The effects of various types of flame exposed to phlogiston are as follows. All examples are for the item being lit or already lit upon exposure.
Oil Flask-6d6-Area 1
Cooking Fire-8d6-Close Burst 1
Fire Keyword-3xNormal-3xNormal or Burst 2
These effects occur immediately and extinguish the effect instantly. For example, lighting a flask of oil to use as an incendiary weapon will cause it to explode immediately. (Actually, a character would have to be extremely tricky and careful even to get that far. The phlogiston would ignite as soon as a flame was created with which to ignite the oil.) The fire resulting from a Fire power with either the fire Keyword or that does fire damage is centered on the wizard casting the spell, even if the effect is centered on another target, the magical nature of the Phlogiston means that it is reacting to more then just the literal flames, and is ignited by the actual magical power creating the flames in these cases.
Because of the nature of the phlogiston, all flaming light sources are extinguished by the crew before entering the flow. Phlogiston is radiant, so no other lights are needed on the exposed decks. Below decks, or in rare (and haunted) Dark Regions of space, cold natural lights (moths or fireflies, fluorescent moss) or magical lights are used for illumination. The heart of dwarven mountain-craft are without running lights, since dwarves have infravision.
Voyagers can move along the rivers of phlogiston at random or according to planned course. Many of these rivers flow in both directions between two crystal shells. In some cases, a river flows in one direction only, forcing the voyager to follow a different course when returning home.
The crystal spheres bob in the phlogiston like corks in an ocean (mind-boggling, enormous corks, but they do bob). As a result, over time the spheres actually shift their positions relative to each other. This almost never changes the courses of the rivers, however, so navigation is possible. But just because a ship passed certain landmarks on its way from A to B does not mean the ship will pass those same landmarks on its way back to A from B. Fortunately, when crystal shells drift too close, the phlogiston between them thickens to the point where the two massive spheres are moved apart and a collision is prevented.
All forms of extra-dimensional powers do not work while in the phlogiston. This includes, summons, communes, teleporting, most forms of divination, bags of holding, and anything else that creates, uses, accesses or works through a diffrent dimension, no matter how weakly or short. Even the most powerful magics known to man are only able to access extra-dimensional spaces for brief seconds while in the phlogiston.
The phlogiston also has special effects on crews when the atmosphere goes deadly. Instead of dying the individual lapses into suspended animation until the atmosphere around him is recharged. Living flesh turns gray and stonelike and remains that way until the individual is rescued. By following along the flow, a ship or individual will eventually drift near a sphere, where recovery is at least possible. Note that rescue is not necessarily by someone with good intentions.