In a D&D game, adventures can unfold in any corner of the multiverse—not just in the dungeons and wildernesses of the Material Plane but also on other planes of existence, including what celestial navigators refer to as Wildspace. When you stand on a Material Plane world and look up at the night sky, what you're seeing is Wildspace and, beyond that, the Astral Sea. Exploring these realms and the worlds they surround is the crux of a Spelljammer campaign.
The Astral Plane is, quite literally, the plane of stars. More precisely, it is where the stars and portals to the heavens reside—an infinitely vast celestial void that surrounds all the worlds of the Material Plane.
Every D&D world—whether round, flat, or some other shape—exists in an airless void known as Wildspace. A world might be solitary, or it might have neighbors: one or more suns, worlds, moons, asteroids, comets, or other bodies. This neighborhood of celestial and planetary bodies is called a Wildspace system.
In Wildspace, the Material Plane and the Astral Plane overlap. Creatures and objects in Wildspace age normally and are effectively on both of those planes at once. If you were to leave your home world and continue outward until you neared the edge of your Wildspace system, you would begin to see a faint, silvery haze. By traveling into this haze, you pass from Wildspace into the Astral Sea, more colorfully known as the Silver Void. The deeper into the Astral Sea you travel, the thicker and brighter the haze becomes, but the stars that shine through it are always visible. Wildspace and the Astral Sea together comprise the Astral Plane.
The Astral Sea, like Wildspace, is a void; however, it is not an airless one. Here, you can breathe normally and exist indefinitely, never aging and never needing food or drink. You can propel yourself through the Astral Sea with the power of your mind alone, though many astral voyagers wisely travel in well-armed ships, for this place is the home of a host of fearsome creatures. Here travelers might find the petrified hulks of dead gods and swirling pools of color that serve as portals to other planes of existence. (For more information about color pools, see The Astral Plane.)
Much in the way that oars and strong winds enable travel by sea on terrestrial worlds, magic items called spelljamming helms are used to propel and steer ships through Wildspace and the Astral Sea. A spelljamming helm customarily takes the form of an ornate chair in which the ship's pilot sits. To attune to a spelljamming helm, one must be a spellcaster. The pilot of a spelljamming ship is called a spelljammer.
Spelljamming is the act of using a spelljamming helm to propel and maneuver a ship.
When cruising through space, a spelljamming ship can travel 100 million miles in 24 hours. At this speed, the spelljamming helm makes minor course corrections on its own to avoid collisions with meteorites, other detritus, and space-dwelling creatures. These slight course corrections sometimes cause mild space sickness, which is a harmless affliction common among those who aren't accustomed to space travel.
A spelljamming ship automatically slows to its flying speed when it comes within 1 mile of something weighing 1 ton or more, such as another ship, a kindori, an asteroid, or a planet. While moving at its flying speed, a spelljamming ship is generally as maneuverable as a seafaring vessel of a similar size. A spelljamming ship moving at its flying speed can accelerate to its 100-million-miles-every-24-hours speed provided there is nothing weighing 1 ton or more within 1 mile of the ship.
Using a spelljamming helm to move a ship produces a feeling in the spelljammer similar to moving a limb that has fallen asleep—a pins-and-needles sensation, though not as painful as its analog. When the ship approaches something large in space, the spelljammer is usually the first to detect it as the ship slows down. An experienced spelljammer can often sense what caused the ship to slow down a few moments before it can be seen; an asteroid "feels" different from a space galleon or a pod of kindori, for example.
A ship can have more than one spelljamming helm aboard it, but only one spelljamming helm at a time can be used to control the ship. If a spelljammer tries to gain control of a ship by using a second spelljamming helm, a spelljammer duel ensues. Resolve this conflict by having each spelljammer make a Constitution check; if the dueling spelljammers tie, have them reroll. The spelljammer with the lowest check result loses the duel and gains 1d4 levels of exhaustion; in addition, their attunement to their spelljamming helm ends at once, and they can't attune to any spelljamming helm until all levels of exhaustion are removed from them.
When a creature or an object leaves a planet's atmosphere and enters Wildspace, an envelope of breathable air forms around it and lasts until that air is depleted.
The envelope of breathable air that forms around a creature takes the shape of a cube centered on that creature. The creature's size determines the cube's dimensions, as shown in the Air Envelopes of Creatures table.
| Air Envelopes of Creatures | |
| Creature's Size | Air Envelope |
| Tiny | 2½-foot cube |
| Small or Medium | 5-foot cube |
| Large | 10-foot cube |
| Huge | 15-foot cube |
| Gargantuan | 20-foot cube |
A creature that needs to breathe will exhaust the air in its personal envelope in 1 minute. Since this is barely enough time to get anywhere, most creatures travel through Wildspace aboard spelljamming ships, which have much larger air envelopes.
The envelope of breathable air that forms around an object extends out from its surface a distance equal to the longest dimension of its form. For example, a spherical planet 5,000 miles in diameter has an air envelope 15,000 miles in diameter, with the planet at the center of it. An air envelope need not be spherical; for example, a block of wood 1 foot by 2 feet by 3 feet is surrounded by a more-or-less rectangular envelope of air 3 feet by 6 feet by 9 feet. The air envelope around a spelljamming ship typically has an ovoid shape.
The air envelope around a habitable planet or moon is called an atmosphere. An atmosphere is a special kind of air envelope that replenishes itself constantly. A creature or an object can refresh its air envelope by entering the atmosphere of a planet or moon (see "Overlapping Air Envelopes" below).
Fire in Wildspace
Although nonmagical fire cannot exist in the vacuum of Wildspace, magical fire (such as that created by a Fireball spell) does burn in a vacuum. Magical fire does not cause objects to burst into flame, however, because there is no air to make ignition possible.
The air envelope around a body or ship can be fresh, foul, or deadly. Air can change from one quality to another over time.
Fresh Air is completely breathable. Under normal circumstances, the air envelope of a ship remains fresh for 120 days. If a ship carries more creatures than its normal crew complement, they exhaust the supply of fresh air more quickly.
Foul Air is stale and partially depleted. It is humid and smells bad. Any creature that breathes foul air becomes poisoned until it breathes fresh air again. The air aboard a ship with a normal crew complement degrades from fresh to foul on day 121, and the foul air turns deadly 120 days later.
Deadly Air is unbreathable. Any creature that tries to breathe deadly air begins to suffocate.
When two bodies come close enough to each other, their air envelopes merge, and the quality of the air around the smaller body changes to match that of the larger body. When the bodies later move away from each other, each one reclaims and retains its own air envelope.
For example, if a damselfly ship with a foul air envelope enters the atmosphere a planet with fresh air, the two air envelopes merge, and the damselfly ship's air quality changes from foul to fresh. If that ship then merges its fresh air envelope with the deadly air envelope surrounding a derelict ship, the damselfly ship's air quality would change from fresh to deadly.
The reason everything pulls its own atmosphere along through space is the force of gravity. It's also the reason why creatures can stand on a spacefaring ship without falling off the deck.
In Wildspace and on the Astral Plane, gravity is an accommodating force, in that the direction of its effect seems to be "that which is most convenient." For an object the size of a planet or moon, gravity pulls everything toward the center of the body, meaning that creatures can stand upright anywhere on the surface, and dropped objects fall perpendicular to the surface they land on.
For smaller objects, such as spacecraft, gravity doesn't radiate from a point but rather from a plane that cuts horizontally through the object and extends out as far as its air envelope. An object's gravity plane is two-directional: a creature can stand upright on the bottom of a ship's hull—upside down from the perspective of those elsewhere on the ship—and move around as easily as if it were walking on the top deck.
One of the unusual properties of a gravity plane is that an object that falls off the side of a ship can end up oscillating back and forth across the gravity plane. It drops in one direction until it crosses the plane, then reverses direction back toward the plane again, continuing until something causes it to stop.
When gravity planes intersect, such as when two ships pass close to each other and at different angles, the gravity planes of both ships remain in effect until the two ships touch one other (as often happens when they collide or when one ship lands on the other). If that happens, the gravity plane of the ship that has more hit points remaining (regardless of the ships' actual dimensions) overrides the other ship's gravity plane, suppressing it as long as the ships remain in contact, and the first ship's definition of "up" becomes the other ship's as well.
When a ship touches down on a planet (or some other enormous body), the ship's gravity plane is suppressed. If a ship has one or more decks on the ventral side of the ship's gravity plane (rather than its dorsal side), precautions must be taken before the ship lands to secure anyone and anything that might fall when the ship's gravity plane is suppressed.
When a spelljamming ship moves in space, creatures and objects in its air envelope move with it, pulled along with the ship because of the strength of its gravity plane.
However, an unanchored creature or object floating in a ship's air envelope is weightless and drifts toward the edge of the air envelope at a speed of 10 feet per minute. For example, an unconscious sailor or a crate that falls off the deck of a spelljamming ship would begin drifting away from the ship along its gravity plane toward the edge of the ship's air envelope. When it exits the air envelope, the sailor or the crate would be left behind as the ship moves away from it.
A floating creature that enters the air envelope of a larger body is immediately affected by the larger body's gravity (such as that of a planet) or gravity plane (such as that of a spelljamming ship). The creature falls from where it entered the air envelope to the surface of that body, or to the gravity plane of that body, whichever is nearer. Normal damage from the fall applies if the creature hits something solid at the end of the fall. A creature or an object that falls across a gravity plane takes no damage from the fall but begins oscillating from one side of the gravity plane to the other, as described above.
Every world of the Material Plane is situated in Wildspace, or more precisely, in its own Wildspace system. Wildspace systems are airless oceans teeming with space-dwelling life forms, including spores, space plankton, and larger creatures that resemble fish and aquatic mammals. The ones that need air to survive either generate their own air envelopes or live in the air envelopes of other creatures.
Wildspace is where the Astral Plane overlaps with the Material Plane. Creatures and objects in Wildspace age normally and exist on both planes simultaneously. This overlap enables creatures to use spells such as teleport and teleportation circle to travel from Wildspace to a nearby world, or vice versa.
The Astral Sea surrounds all the Wildspace systems, as well as the astral dominions of gods and the floating remains of dead gods. Many Wildspace systems have names; for example, Realmspace is a Wildspace system that contains, among other things, the planet Toril—home of the Forgotten Realms setting.
Astral Dominions and Dead Gods
Many gods have dominions in the Astral Sea. These locations typically take the form of floating islands or cities of fantastic proportions. Astral travelers might visit these dominions as they would any other ports of call, though a dominion's divine ruler always knows when visitors have arrived and what their intentions are. Because these dominions are part of the Astral Sea, they are timeless; nothing ages there, and creatures can survive there indefinitely without food or drink.
The Astral Sea is also where one can find the petrified remains of gods who were slain by more powerful entities or who lost all their mortal worshipers and perished as a result. A dead god looks like a gigantic, nondescript stone statue that bears little resemblance to the divine entity it once was. Githyanki, mind flayers, psurlons, and other natives of the Astral Plane sometimes turn these drifting hulks into outposts and cities, many of which are hollowed out beneath the surface.
The following sections describe how astral travelers can get from one Wildspace system to another, as well as features of the Astral Plane that are likely to come into play.
A typical Wildspace system has a sun plus a number of planets and moons orbiting it. World-to-world travel requires a spelljamming ship, a teleport spell, or some other kind of magic. Within a Wildspace system, the DM must decide how long it takes a spelljamming ship to travel from one world to another. This task is made easier if the DM has a diagram that shows how far away each world is from the center of the system. Using such a diagram, you can calculate the shortest possible voyage (when the two worlds are as close to one another as possible) and longest possible voyage (when the two worlds are as far apart as they can be).
Tracking Time in Wildspace
Local time varies from world to world and from one Wildspace system to the next, depending on rotational periods, custom, and a host of other factors. Astral travelers often rely on what is considered the standard way of keeping time.
A standard day is 24 hours long. A standard week is seven standard days, and a standard month is four standard weeks (28 standard days).
The typical method for determining the length of a year—the amount of time that passes during a complete cycle of the seasons—has no meaning or usefulness for individuals who spend most of their time on the Astral Plane. For this reason, astral travelers avoid using years as a measurement of time.
A creature or ship that wants to travel from one Wildspace system to another must cross the Astral Sea unless it has some other magical means of traveling from one world in the multiverse to another.
Wildspace systems aren't fixed in certain locations in the multiverse. Because they're constantly in motion, like corks bobbing in water, no reliable devices exist to help plot a course from one Wildspace system to another. Fortunately for travelers, the nature of the Astral Sea makes such journeys relatively easy, as discussed in the next section.
The Astral Sea not only has gravity but also breathable, comfortable air. But is the air real, or does this heavenly realm merely trick creatures into thinking they're breathing? In the Astral Sea, one can never be certain. All that really matters is that a creature can survive indefinitely in the Astral Sea, never aging and never feeling hunger or thirst.
A creature doesn't need a vessel to travel through the Astral Sea. In this realm, a traveler has the option of propelling itself by thought alone. The more intelligent a creature is, the faster it can move. A creature that chooses to move in this fashion can move in any direction at a flying speed in feet equal to 5 × its Intelligence score.
One doesn't need a map to navigate the Astral Sea. Here, all creatures are blessed with directional awareness. In other words, a creature can get to where it wants to go by thinking of its destination, at which point it becomes aware of the most direct route to that location. The destination must be somewhere in the Astral Sea or in Wildspace, such as "the nearest githyanki outpost," "the astral dominion of Hestavar," or "Realmspace." This directional awareness doesn't reveal how safe the route is, and the DM decides how far away the destination is and how perilous the trek through the Astral Sea is.
The ambient temperature on the Astral Plane is about the same as on a moderate summer day in the temperate region of most worlds. Since there are no seasons in Wildspace or the Astral Sea, this temperature remains constant at all times. Some Wildspace systems, however, have significantly higher or lower temperatures. Krynnspace, for example, has a very low natural temperature (about 16 degrees Fahrenheit), and clouds of ice particles swirl in the vacuum within its boundaries. Of course, as one approaches a star that puts out heat, the ambient temperature increases.
Fishing is a popular pastime in Wildspace and the Astral Sea, though this activity isn't possible aboard a ship that is moving faster than its flying speed (discussed later in this chapter). Wildspace settlements sell basic fishing equipment for 1 sp. For that, you get a pole, a line, a hook, and either a lure or some bait.
At the end of each hour spent fishing, a character can make a DC 15 Wisdom (Survival) check. A failed check indicates no fish is caught during that hour. On a successful check, roll a d10 and consult the Fishing table to determine the catch.
| Astral Fishing | |
| d10 | Catch |
| 1-2 | Tiny, inedible fish (a creature that consumes it is poisoned for 1 hour) |
| 3-5 | Tiny, edible fish (feeds one person) |
| 6-8 | Small, edible fish (feeds up to four people) |
| 9 | Hostile space eel (feeds up to twelve people when defeated) |
| 10 | Hostile gray scavver (feeds up to twenty people when defeated), some other creature of the DM's choosing, or an Tiny object of the DM's choosing |
Because of the way gravity can change and fluctuate while traveling through wildspace and astral space, there are a few special circumstances that can arise.
In any location where gravity isn't present, the following rules apply:
Impeded Melee. When making a melee attack with a weapon, a creature that doesn't have a flying or swimming speed (either naturally or provided by magic) has disadvantage on the attack roll unless the weapon deals piercing damage.
Movement. A creature can use an action to push off something heavier than itself and move up to its walking, flying, or swimming speed in a straight line. The creature continues along this course, moving in a straight line at its speed on each of its turns until something stops it or changes its trajectory.
The ranges of ranged weapons are halved, as are all jump distances. When a creature makes its first attack in a round using a weapon that has the Heavy property, it makes a DC 12 Strength or Constitution (Athletics) check or subtracts 1d4 from its attack rolls for 1 round. Falling damage is treated as twice the distance in the area and there is no maximum amount of damage that can be taken from a fall. For every hour beyond the first spent in the area, a creature not acclimated to it makes a Constitution saving throw (DC8 + the number of hours spent in the area) or gain a level of Exhaustion. Exhaustion gained due to high gravity cannot exceed 3 levels of Exhaustion.
The ranges of ranged weapons are doubled, as are all jump distances. Falling damage is treated as half the distance in the area. In addition, damage from bludgeoning weapons is reduced by half.