Chapter 2: Astral Adventuring
Source: Astral Adventurer’s Guide, p. 17
If you’re a player or a Dungeon Master who wants to know more about spelljamming and the Astral Plane, this chapter is for you. It expands on what’s written about the “Astral Plane” in the “Dungeon Master’s Guide” and includes an assortment of spells, magic items, and spelljamming ships.
How Spelljamming Works
Spelljamming is the act of using a spelljamming helm (“described later” in the chapter) to propel and maneuver a ship. The individual that operates the helm is called a spelljammer.
Speed
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 (discussed later in this chapter) when it comes within 1 mile of something weighing 1 ton or more, such as another ship, a kindori (see “Boo’s Astral Menagerie”), 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.
Sensations
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.
Spelljammer Duels
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.
Air Envelopes
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.
Air Envelopes of Creatures
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.
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.
Air Envelopes of Objects
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. “Diagram 2.1” shows the air envelope that surrounds a nautiloid that has a keel length of 180 feet. It extends 180 feet from the ship in all directions.
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.
Air Quality
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 (see the rules on “suffocation” in the “Player’s Handbook”).
Overlapping Air Envelopes
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.
Gravity Planes
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. “Diagram 2.1” shows the location of the gravity plane of a nautiloid, by way of example, and indicates the directions in which its gravity operates.
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.
Overlapping Gravity Planes
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.
Drifting
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.
Falling
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.
The Astral Plane
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.
Diagram 2.2 illustrates how the Astral Sea surrounds all the Wildspace systems, as well as the astral dominions of gods and the floating remains of dead gods (see the “Astral Dominions and Dead Gods” sidebar). 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.
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.
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.
Creating a Wildspace System
A typical Wildspace system has a sun plus a number of planets and moons orbiting it. Two examples of Wildspace systems, Doomspace and Xaryxispace, are described in the accompanying adventure, Light of Xaryxis. Use them as models when creating your own Wildspace system.
Travel between Worlds
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 (the diagrams of Doomspace and Xaryxispace in Light of Xaryxis serve as examples). 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).
Travel between Systems
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.
Traversing the Astral Sea
The Astral Sea not only has gravity (see ""Gravity Planes"" above) 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.
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.
Travel by Thought Alone
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.
Astral Sea Navigation
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.
Temperature
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.
Astral Fishing
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.
Weightlessness
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.
Magic
Magic functions on the Astral Plane as it does in most other D&D settings. The following sections present spells and magic items that are popular among astral travelers.
Spells
The Spells table shows which classes can cast the spells in this section and the levels of those spells. The table also notes the school of magic of a spell and which classes have access to it. (The artificer class is presented in “Tasha’s Cauldron of Everything”.)
Magic Items
This section describes magic items that are essential to travel and survival in Wildspace, as well as other items likely to be found on the Astral Plane.
Spelljamming Ships
This section provides descriptions of various spelljamming vessels and rules that can be used when running encounters aboard them.
