The Material Plane is where the various planets and solar systems of the Aethervane universe can be found. Most of the sentient races and other creatures of the Aetherverse originate on these worlds. The Material Plane is also the most common destination for spelljammers. This is because other more exotic planes tend to be difficult or even outright impossible for spelljammers to navigate.
In 1494 DR, the layout of the Material Plane in the Aethervane universe was completely altered by a cataclysm of universal proportions. The cataclysm corresponds in the real world to the release of the 5th edition D&D Spelljammer books, aligning the Aetherverse with the newly published official lore and mechanics.
A full description of how the Material Plane currently works in the Aetherverse can be found in the Astral Adventurer's Guide (page 4 and pages 17-22).
For the sake of reference, the previous arrangement of the Material Plane (before the Cataclysm) has been preserved below. The lore and mechanics here no longer apply to the current state of the Aethervane universe.
Each solar system in the Material Plane is encased within a sort of bubble known as a Crystal Sphere. The radius of the Sphere is typically around 5 billion miles and twice the distance between the system's center and the farthest celestial body. Despite their massive size, Crystal Spheres exert no gravitational pull.
The surface of a Crystal Sphere has an iridescent, filmy quality, much like that of a soap bubble, but it is completely impenetrable. The only way to pass directly into or out of a Sphere is through openings that appear and vanish at random on the Sphere's surface. It is also possible to find portals that lead from other dimensions, such as the Astral Plane, directly into the interior of a Crystal Sphere.
Most Crystal Spheres are transparent. From the outside, even from a great distance, a viewer can see the sun at the center of the system (assuming it has one), as well as any other light-emitting bodies, such as fire planets. From inside a Sphere, the viewer can see the stars and lights shining from within other Spheres in the cosmic neighborhood.
The Crystal Spheres are distributed mostly along a single plane with only slight three-dimensional variation in placement, giving the appearance of a galaxy. For that reason, the Material Plane is sometimes referred to as “the galaxy.” It is possible that other galaxies exist, or perhaps even entirely separate Material Planes, but if so, no solid evidence or proof of their existence has yet been discovered.
The laws of physics can vary from one Crystal Sphere to another. Gravity and air envelopes do not necessarily work the same way within every Sphere. Certain Spheres may have unique or even bizarre shapes and configurations of worlds, such as ring-shaped planets or flat worlds borne atop the backs of massive celestial beasts. Gunpowder, in particular, is notorious for behaving unpredictably from Sphere to Sphere; as a result, most spelljamming crews shun the use (or even the transportation) of cannons and firearms.
The void between the celestial bodies inside a Crystal Sphere is called Wildspace. It behaves similarly to outer space with a couple of notable exceptions:
Crystal Spheres typically contain solar systems made up of a variety of celestial bodies. Any bodies at the center of the system are referred to as “primary.”
Celestial bodies come in at least 5 major types:
Although celestial bodies are most often spherical, they can also be cubic, elliptical, flat, toroidal, or even broken up into clusters or belts.
The following categories help to quickly give a sense of a celestial body's size:
| Size | Maximum Diameter | Example Objects | Original Spelljammer Classification |
|---|---|---|---|
| Tiny | 100 miles | asteroid, comet | A, B |
| Small | 1,000 miles | small moon | C |
| Medium | 10,000 miles | large moon, Earth-sized planet | D, E |
| Large | 100,000 miles | gas giant | F, G |
| Huge | 1 million miles | medium star | H |
| Gargantuan | 1 billion miles | large star | I, J |
Outside the Crystal Spheres is a swirling (and extremely flammable) gas called the Phlogiston or the Flow. Although the Phlogiston appears as an array of fluorescent rainbow hues up close, from farther away, it is invisible. Thus, from inside a Crystal Sphere, a viewer looking out into the Flow sees only a black sky dotted by the various stars and other luminescent celestial bodies of the galaxy.
The Flow behaves exactly as Wildspace does with the following additions:
Most planets and certain other celestial bodies on the Material Plane possess a breathable atmosphere that naturally replenishes itself over time. All creatures and objects that come in contact with such an atmosphere carry an “envelope” of air with them when they leave. This means that the crews of spelljammers don't need to worry about finding breathable air as they travel through the Wildspace or the Flow of the Material Plane, and even if an individual leaves the ship while traveling through the void, they can survive for some time before they run out of air.
Note that the entire Astral Plane is filled with a breathable air-like medium. Creatures and crews do not need to worry about air supply there. Air supply is only a concern in the Flow and in Wildspace.
The air envelope around a creature or object forms an oval spheroid whose length and width at their greatest extents are three times that of the object itself. For example, a ship that is 100 ft long has an air envelope that extends 100 ft in front of it and 100 ft behind it, making the entire envelope 300 ft long. And if that same ship is 50 ft wide, the envelope extends 50 ft to each side, making the entire envelope 150 ft wide.
The envelope around an individual creature is enough to allow the creature to breathe for about 10 minutes. After that time has elapsed, they begin to suffocate.
Each ship has a maximum creature capacity and carries enough air in its envelope to support that many Medium creatures for about 4 months. Each time the ship's envelope comes into contact with another atmosphere, the two atmospheres blend together. In this way, ships can replenish their envelopes whenever they dock at a planet or similar harbor.
All objects that are of Gargantuan size (20 ft or larger in any dimension) exert gravity equal to Earth within a radius equal to that of the object's air envelope. Outside of that radius, an object's gravitational attraction is the same as it would be in normal physics.
The gravity of an object does not necessarily pull objects toward its center. Ships and small celestial bodies (like asteroids) typically have a “gravity plane," a 2-dimensional plane that bisects some point of the object, often its center or its base.
The gravity plane extends to the edge of the object's air envelope. Creatures and objects within the air envelope are attracted to the gravity plane from both above and below. If you fall “past” the plane, you are attracted back up to it, “bobbing” up and down until you reach an equilibrium and come to rest at a point level with the plane.
Creatures and objects that are not standing on or clinging to an anchored object are pushed slowly toward the outside edge of a gravity plane.
Where planes of gravity intersect, the larger plane takes over. This applies only to the intersection point itself, however. Non-intersecting points of a gravity plane remain in effect even while close to a more powerful gravity plane. Once the gravitational objects come into physical contact, however, the larger gravity plane completely overrides the smaller one.
Ships generally approach each other so that they are both “rightside up” relative to each other and on more or less the same horizontal plane, as this makes communication easier and minimizes the chance of a confusing collision of gravity planes. However, a larger ship could specifically approach at a different angle in an attempt to use its own plane as a form of “attack” (causing the people on the smaller ship to “fall” off their ship toward the plane of the larger ship).
Fighting while weightless presents disadvantage on attacks and attacks against you have advantage. Nonmagical movement while weightless is only possible by pushing off of something or throwing objects and can be considered essentially to be movement through difficult terrain. Missiles travel forever outside of a gravity plane and an air envelope.