Spelljammers are airships that sail through not only the skies but also the voids of the Astral Plane and the Material Plane. When in the absence of planets and other objects that exert a gravitational pull, spelljammers can reach incredible speeds, traversing millions of miles in mere hours. A spelljammer can look like just about anything, but they typically resemble sailing ships or marine creatures, as many of the first cultures to build spelljammers drew from more familiar nautical traditions when designing their spacefaring vessels.
Below are more detailed rules regarding spelljammers. It is not necessary for DMs to follow these rules to the letter. As you plan and run adventures, feel free to deviate from these mechanics (within reason).
Note that these rules were designed prior to the release of the 5th edition D&D Spelljammer books. Many of the mechanics below contradict the current “official” mechanics of spelljammers. Rather than revise all of the previous mechanics, they have been preserved below in their original form for the sake of reference. The “official” 5th edition mechanics are described in the Astral Adventurer's Guide. It is up to each DM to decide which version of the spelljamming mechanics to use—the 5th edition ruleset, the legacy Aethervane mechanics, or something else entirely.
Spelljammers are usually between 20 and 300 feet long. Even the smallest ships fall into the Gargantuan size category.
While the length and width of a ship tell you its precise dimensions, tonnage is a more mechanically-oriented measure of a ship's carrying capacity.
Depending on its tonnage, a spelljammer will fall into one of the following 4 classes.
Spelljammers have a maximum number of crew and passengers (creatures of Small or Medium size) that can comfortably fit on board, which is equal to the ship's tonnage. For the purposes of determining capacity, a Large creature counts as 2 Medium creatures, and a Huge creature counts as 3 Medium creatures. 2 Tiny creatures can occupy the same space as a single Medium creature.
It is possible for a spelljammer to carry more creatures than its capacity, but the additional creatures must occupy the areas of the ship normally intended for cargo, and they will strain the ship's air supply (although, within the context of a single adventure, air supply is unlikely to come into play). For every Small or Medium creature beyond the ship's capacity, subtract 1 ton from the ship's available cargo space.
A spelljammer's cargo rating indicates how many tons of equipment and materials it can carry. For the purposes of this campaign, 1 ton is equal to a 5-ft cube or an object of Medium size. If a ship is loaded with more cargo than it can carry, each point of additional cargo subtracts from the ship's creature capacity.
The cargo rating also determines the maximum total tonnage of the ship's weapons. These attachments do not subtract from the ship's cargo space, but their total tonnage cannot be higher than the ship's cargo rating.
Spelljammers carry an envelope of breathable air with them as they travel. If there are no more creatures on board than the ship's capacity, the air supply lasts about 4 months. If the creatures on board exceed the ship's capacity, the supply lasts about 2 months.
Within this envelope, spelljammers also project a plane of Earthlike gravitational force, typically bisecting the ship lengthwise, which attracts creatures and objects from above and below.
The air envelope and gravity plane remains intact even when a spelljammer enters the Astral Plane, which generally contains neither air nor gravity.
More information on air envelopes and gravity planes can be found on the Material Plane page of the wiki.
The value of a spelljammer is measured in gold pieces (gp). This is not necessarily the actual selling price of the ship, but rather a scale with which to rate the relative power of each spelljammer as compared to others.
In the Aethervane campaign, spelljammers are treated in the same way that other permanent magical items are. Each spelljammer is assigned a rarity from uncommon to legendary. This helps DMs decide when it is appropriate to allow a PC to acquire a spelljammer as an adventure award, and it also restricts the characters who are able to use it according to their level (see “Attunement,” below).
Each spelljammer is powered by a magical artifact known as a helm. The helm allows a pilot (or, in some cases, more than one pilot) to propel and steer the ship. With few exceptions, helms provide propulsion only within the Material Plane. For moving through the Astral Plane, spelljammers generally rely on rigging (see below).
Like the spelljammers they are a part of, helms take on a wide variety of appearances, most commonly a throne-like seat located somewhere in a well-protected area of the vessel. The helm is intrinsically linked to its vessel. The only way to move a helm to a different vessel is to completely refit the new vessel, a process that is nearly as expensive as building a new vessel from scratch.
Using the spelljammer's helm requires attunement by a character with the appropriate maximum number of hit dice, depending on the ship's rarity. Any character can attune to an uncommon spelljammer. A character must have at least 5 hit dice to attune to a rare spelljammer. A very rare spelljammer requires a pilot with 11 hit dice or more. A legendary spelljammer requires that the character have at least 17 hit dice, which means that the helm is only accessible to NPCs, unless some sort of exception is made.
In order to attune to a helm, the pilot must remain in physical contact with it for the duration of a short rest.
While using the helm, the pilot must continue to touch it, and must concentrate, as if concentrating on a spell. Most helms are stationary, but there is at least one type of Very Rare helm, called a crown of stars, that allows the pilot to move about the vessel while operating it.
If a pilot concentrates on operating a helm for over 12 hours without taking a long rest, the pilot must make a Constitution saving throw after each additional hour. The DC is 10 +1 for each hour past 12 hours. On a failed saving throw, the pilot suffers one level of exhaustion. For this reason, it’s a good idea to have multiple pilots for long voyages so that they can operate the helm in shifts.
While operating the helm, the pilot becomes “one with the ship.” There is no need to manipulate controls—the pilot propels and steers the ship by will alone. The pilot remains aware of its own surroundings and can talk to people in the area, but the pilot's sensory perception also extends to the entire spelljammer and the area around it, up to the range of the pilot's normal vision.
There are many variations of helms, and each one has its own unique origin and power source. Several examples are given below, but this is by no means an exhaustive account of all of the forms a helm can take.
The most common type of helm is the mage helm, also known as a spelljamming helm. Mage helms are powered by the mystical energy that all spellcasters can channel. The spellcaster must expend spell slots to activate the helm. The ship remains powered for 12 hours.
The secret of mage helm construction is apparently known only to the arcane, an ancient race of giant, blue-skinned, spacefaring merchants who, as far as anyone can tell, exist only to sell mage helms to anyone willing to pay for them. It is a vexing mystery as to how the arcane learned these secrets or what they do with the profits.
Gnomish helms are the invention of tinker gnomes from the world of Krynn. The tinker gnomes are the only race that has come close to replicating the mage helms of the arcane. Gnomish helms rely on a convoluted assemblage of gizmos, which (according to every scholar who has attempted to study them) shouldn't work, despite the clear fact that they somehow do… at least most of the time.
Gnomish helms function in the same way as mage helms except that, once per day, the DM may roll a d20. On a result of 1-4, the helm breaks down catastrophically. Before it can be used again, the helm must be repaired by tinker gnomes (or rock gnomes). The repairs take 1-3 hours for a single gnome to complete. Multiple gnomes working together can complete the repairs faster.
A crown of the stars is essentially a portable mage helm, typically taking the shape of a silver crown. It functions as an ordinary mage helm, except that it allows the mage to pilot the ship while moving about, even up to 1 mile away from the ship itself.
A crown of the stars can be used only with a ship specifically built for it. A new ship may be created for the crown, but in that event, the old ship permanently loses its bond to the crown.
Crowns of the stars are exceedingly rare. It would seem that not even the arcane know how to construct them, implying that they are perhaps the relics of some other long-forgotten race.
Chemical helms are powered by physical fuel. They have various origins and as many different forms. The amount and type of fuel needed per hour depends on the helm and the ship’s tonnage.
Regardless of the type of fuel they use, chemical helms are the slowest and least efficient of the helm types. Moreover, any attempt to use a chemical helm that relies on combustion while in the Flow leads to the destruction of the ship and everyone aboard.
Furnace helms melt down magical items for fuel. As with chemical helms, use of a furnace helm in the Flow leads to the destruction of the ship.
It has been theorized that furnace helms were an early invention of the arcane, before they perfected the art of making mage helms. Regardless of their precise origin, it appears that they have fallen out of favor and, as a result, tend to be found only aboard ancient derelicts.
An artifurnace is an advanced furnace helm that draws power from a legendary permanent magic item. Once installed in an artifurnace, the legendary item powers the spelljammer indefinitely. If the item is ever removed, however, the artifurnace is destroyed. Unlike furnace helms, artifurnaces are usable within the Flow.
Artifurnaces tend to be found only aboard ancient ships. Perhaps they represent the culmination of the arcane's early experiments with furnace helms before they turned to producing mage helms.
The spacefaring dwarf clans utilize a unique form of helm that consists of an enormous enchanted forge. The precise method of the forge's construction is a closely guarded dwarven secret, but the clans have been known to claim that the forges were a blessing from one or more dwarf gods. (The specific gods named vary depending on which clan you ask.)
As dwarves use the forge to smith tools, weapons, armor, and works of art, a divine “creative energy” is released that somehow powers the helm and propels the ship. Of the smiths, only 1 attunes to the helm as its pilot. After 12 hours of smithing, all of the smiths (not just the pilot) begin to tire.
Despite the forge helms' dependence on hot fire, they are enchanted to repel the combustible gas of the Flow. Forge helms are usable within the Flow, although flames outside of the forge chamber are still quite capable of sparking an explosion.
Spacefaring mind flayers were the inventors of the series helm, and they remain the primary race that employs them. The only other race that frequently uses series helms are the githyanki, who stole the secrets of the helms' construction when they overthrew their mind flayer overlords. Series helms can be powered only by creatures with innate psychic abilities, like mind flayers and githyanki.
Series helms are not especially powerful. By itself, a single series helm can propel only a Corvette. However, multiple series helms can be attached to the same ship, and by using their power in conjunction, they can propel larger ships. Each helm requires its own individual pilot to be attuned to it. Typically, the pilots share a telepathic bond that allows them to control the ship in unison. If multiple pilots attempt to move the ship in different ways, it stops moving altogether.
Due to their use of psychic energy, series helms are functional even within the Astral Plane.
The mind flayers are also responsible for developing the pool helm. This type of helm consists of a pool in which an elder brain sits. The elder brain must attune to the helm and serves as the ship's sole pilot, propelling the ship with its considerable psychic abilities. Because of its large size, the elder brain occupies 2 slots of the ship's creature capacity.
As with series helms, the pool helm is functional within the Astral Plane as well as the Material Plane.
An orbus is a mutated beholder that serves as a helm. It is blind, with a toothless mouth, withered eye stalks, and milky white skin covering its eyes. The orbus otherwise functions as a series helm that another, unmutated beholder channels its magical energy through in order to pilot the ship. Often, especially when there is more than one beholder on board, a hive mother serves as the pilot and relays orders to the other beholder crew.
A lifejammer is powered by the life force of a (typically unwilling) sacrificial victim. The victim is, for all intents and purposes, the fuel that powers the helm. The victim does not attune to the helm. Another creature must attune to the helm and serve as its pilot.
Lifejammers were invented by the neogi. They are used by the neogi, but also other evil crews that have managed to get their hands on them and are not bothered by the inherent ethical dilemma, such as orcs.
Crystal thrones are helms that were once grown from crystals by ancient spacefaring thri-kreen. This technique has apparently been lost by modern thri-kreen, who have not been seen traveling through space for a long time. All the same, thri-kreen ships are occasionally discovered with their crystal thrones still intact. A crystal throne is usable only by a thri-kreen pilot and is powered by the thri-kreen's psychic abilities.
Like series helms and pool helms, crystal thrones are functional within both the Material Plane and the Astral Plane.
The following movement rules are written with a 100-foot hex map in mind. If playing on such a map, it is recommended that the DM use 1-minute turns instead of 6-second turns, at least until ships close into boarding range. This speeds up play and also simplifies the conversion of movement speed into hex speed. For every 10 feet of movement a ship has, it can move one 100-foot hex per turn. For example, a ship with a movement speed of 70 feet can move 7 hexes.
The movement rules work just as well using 10-foot hexes with standard 6-second rounds. However, since most spelljammers are around 100 feet long or more, they would take up 10 or more hexes on a 10-foot scale map, making them difficult to work with.
Technically, spelljammers can move in all 3 spatial dimensions. Practically speaking, however, while using a flat map, 3-dimensional movement is difficult to accommodate and doesn’t add much interest to the game. If a ship attempts to move up or down to retreat from an enemy, for example, the pursuer will simply move up or down to match. Thus, for all intents and purposes, 3-dimensional movement can be ignored, particularly when using a physical map (as opposed to p laying “in the mind’s eye”). In those specific instances when it becomes impossible to ignore, it can be handled by the DM on a case-by-case basis.
Helms provide two modes of movement: tactical speed and spellspeed.
While moving at tactical speed, the movement rate of the ship is approximately twice that of an ordinary sailing ship.
If the pilot is called upon to make a difficult maneuver, they must make an ability check. The ability used for the check depends on the design of helm they’re using, but the default is Intelligence. As long as the pilot is attuned to the helm, they can add their proficiency bonus to the ability check.
At spellspeed, the ship moves at a rate of millions of miles per hour but is unable to turn. Spellspeed is a magical mode of transportation and is not subject to the laws of inertia. A crew might feel a bit of a kick when their spelljammer accelerates to full speed, but they don’t have to worry about their insides turning to mush or being hurled off deck as their ship accelerates to millions of miles per hour in an instant, or decelerates just as suddenly.
Additionally, the crew does not need to concern themselves with a collision. While traveling at spellspeed, the ship appears as a streak of light to an outside observer, and it phases through any small creatures or objects in its path, causing no damage or effects of any kind to the ship or the object it passed through. However, if the spelljammer attempts to turn or comes within a mile of a creature or object of Gargantuan size (20 ft or larger in any dimension), it automatically slows to tactical speed, and the spelljammer cannot return to full speed until it is farther from the obstacle.
In addition to the helm, most spelljammers are equipped with rigging (sails, fins, and so on). Since helms are generally useless outside of the Material Plane, the rigging is required for travel through the Astral Plane by catching the psychic winds that pervade the plane. For the same reason, most spelljammers are incapable of reaching spellspeed while on the Astral Plane.
Movement via rigging allows the spelljammer to move at approximately the same speed as a normal sailing vessel, and it is dependent on the direction of the psychic winds. When sailing directly against a current, rigging speed is reduced by 50%. When sailing in the same direction a current is moving, rigging speed is increased by 50%.
Fortunately for spelljammers, doldrums in the Astral Plane are exceedingly rare. There is almost always at least a slight psychic wind, and spelljamming crews do not need to worry about being caught “dead in the water.”
The rigging also allows spelljammers to ride the currents of the Flow, as well as mundane air currents. In this way, a typical spelljammer can use its rigging and helm in conjunction while in the Flow or while within a planet's atmosphere. However, rigging is of no help while moving at spellspeed.
A spelljammer cannot immediately accelerate to its full speed or come to a dead stop. A spelljammer can accelerate or decelerate by up to half its movement speed in 1 minute. For example, a ship with a movement speed of 70 feet can alter its speed (up or down) by no more than 35 feet per minute.
Unless a spelljammer is specially equipped, it can only move forward. In order to change direction, the pilot must steer the ship, changing its physical orientation in space. In other words, most ships cannot move in reverse or sideways or directly up or down relative to their orientation; the ship must point in the direction it is moving.
A ship's turn radius indicates how sharply it can turn at once. When using a hex map, a ship can change its facing up to its turn radius, and then it must move at least 1 hex forward before turning again. Each turn expends 1 hex of movement.
|Turn Radius||Maximum Change in Hex Facing Per Turn||Minimum Hexes of Movement Between Each Turn|
The landing property indicates whether a spelljammer is capable of landing on water, on land, on both, or on neither.
When one ship crashes into another, they both stop moving. The ramming (instigating) ship must make a DC 10 Constitution saving throw. On a failed save, it takes 88 (16d10) bludgeoning damage. The target ship (the one that was struck) must make a Dexterity saving throw with a DC equal to 10 + the ramming ship’s Strength modifier. On a failed save, the target ship takes 88 (16d10) bludgeoning damage, or half as much damage on a successful one.
A spelljammer's armor class is determined primarily by the hardness of the material that makes up its hull. Most spelljammers are made of wood and have AC 15.
Spelljammers usually have between 10 and 3,000 hit points, based on their tonnage.
Based on the ship's class, it will have a damage threshold between 10 and 25. Any damage dealt to the ship below its threshold is ignored.
Each spelljammer has ability scores for Strength, Dexterity, and Constitution. These scores are based on the ship's class and are used primarily when rolling for saving throws and initiative. A ship's Dexterity score has no effect on its armor class. Likewise, a ship's Constitution is not related to its hit points.
Spelljammers can be outfitted with a number of siege weapons. Stats for the ballista, cannon, mangonel, and trebuchet can be found on pages 255-256 of the Dungeon Master's Guide. Rules for using jettisons and rams are provided below.
Note that just having a weapon mounted on a ship is not enough to enable it to attack every turn. First of all, each weapon must be attended to by a certain number of crew members (shown in the ship's statblock). Secondly, a weapon can only attack in the direction it is mounted. For example, if a ballista is mounted to the front of a ship, it can only target enemies that lie in front of the ship.
Cannons and firearms are rarely used aboard spelljammers, as carrying gunpowder through the Flow is nigh suicidal, and shifts in local physics between Crystal Spheres can also produce unpredictable results in combustion-based weapons.
A jettison is an anti-personnel siege weapon that resembles a mangonel, but instead of a single stone, it launches a cloud of debris at a ship in close range. Although the debris does not hit with enough force to damage a ship's hull, it can devastate an unprepared and exposed crew.
Before the jettison can be fired, it must be loaded and aimed. It takes 1 action to load the weapon, 1 action to aim it, and 1 action to fire it.
The jettison targets all exposed creatures on the deck of a ship within 100 feet of it. All targets must make a DC 11 Dexterity saving throw. On a failed save, a target takes 11 (2d10) bludgeoning damage.
If a ship that collides with another is equipped with a ram, it makes its Constitution saving throw with advantage, and any damage that would be dealt to the ramming ship is dealt to the ram instead. The ram has 100 hit points. If the damage exceeds the ram’s current hit points, the ram is destroyed and the excess damage carries over to the ramming ship’s hull.
A piercing ram has the same stats as a blunt ram, except that it deals piercing damage instead of bludgeoning damage. Also, if the ram is not destroyed and if the target ship fails its Dexterity saving throw, both ships become grappled.
A grappling ram has the same stats as a blunt ram, except that it deals piercing damage instead of bludgeoning damage. Also, if the ram is not destroyed and if the target ship fails its Dexterity saving throw, the target ship becomes grappled.
Anchors are used to moor a ship to a larger body, such as an asteroid, or to tie two ships together. Anchors are also used at space docks to secure ships and keep them from drifting off.
Lifeboats are hard-shelled vehicles designed to bring their occupants to the surface of a planet or to a rescue ship in relative safety. The lifeboat falls toward the nearest gravity well. Once landed, it will never fly again.
A lifeboat takes up as much cargo tonnage space as one-half the number of people it can carry. Collapsible lifeboats can shrink up to 1 ton of space but require 5 (2d4) minutes of setup before they can be launched.