Spelljammer, Magic

by Kamebit

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Spelljammer Primer


The vast void that lies between the planets and the stars is called wildspace. These regions are primarily empty expanses, but the cosmos is large and vast with plenty of exceptions to the rules. Adventure is the only constant.

Air as a resource

The void of wildspace holds things together and is why planets and moons can sustain enough air to sustain life. It is also how ships can hold enough air for their crew.

Air Units, Vaati

The typical air unit spelljammers use is the vaati (named after Wind Dukes of Aaqa). One vaati is the amount of air a small or medium creature requires to survive for 24 hours. This table shows the amount of air a creature consumes.

Tiny 1/2 Large 4
Small 1 Huge 8
Medium 1 Gargantuan 16+
Air envelopes

The air envelope of a ship extends out from the edges of the hull in all directions for a distance equal in length to the vessel's beam, so that creatures aboard and near the ship can breathe normally in space.

Just like ships, creatures and objects carry air envelops with them in wildspace. When a creature leaves an atmosphere of fresh air it carries enough air with it to sustain itself for a minute. A creature that suddenly is ejected into the void carries only a poor air envelope that will last only 2d4 rounds.

If two creatures physically interact for a round, the air envelopes of both will merge and be redistributed equally in among both creatures.

Foul air

Living creatures consume air, and once an air envelop is mostly consumed the air is no longer suitable and creatures in foul air become progressively exhausted until they die. After a day of rest or an hour of physical labor, such as manning a ship, a creature must make a Constitution saving throw against a DC 15 or take a level of exhaustion.

While in foul air, creatures cannot recover levels of exhaustion, even with appropriate food and water.

Air Taxes

Inhabited wildspace centers and citadels charge an air tax of 1 gp per medium or small creature upon docking, and an additional 1 gp for each additional week. These fees are used by authorities to replenish air and other resources.


Wildspace is typically not extremely hot or cold unless in proximity to a star, where temperatures can raise or even drop suddenly. The temperature within the air envelope is 70 degrees Fahrenheit.

Special Wildspace

As a GM be sure to spice up your vast voids of wildspace with variations in "terrain", such as the following.

Shadow Space. There are expanses where the bleakness of the Shadowfell leaks into wildspace. In these area light is quenched. Bright light becomes Dim light, and Dim light becomes total Darkness. Temperatures also drop to extreme cold (DMG Chapter 5.). Finally undead gain advantage on saves in shadow space.

Blue Oasis. Not all wildspace lacks atmospheres, there are entire stretches that have enough air for millions of planets. These areas normally are blue like the sky, and have winds, clouds and even rain and snow.


A fact most ground lovers are not aware of is that all objects create equivalent gravity pulls. However gravity fields of larger objects override any gravity pull of lesser bodies within their fields. This is why the crew of a ship will have their gravity aligned with that of the ship.

The gravity field while the ship is in the void of space, so that creatures can walk on the ship's decks as they normally would. Creatures and objects that fall overboard bob in a gravity plane that extends out from the main deck for a distance equal in length to the vessel's beam.

Ship pilots tend to align their ships to the larger gravity planes before entering their area of effect, to reduce the effects of gravity change as much as possible. Even then many ground lovers feel the switching of gravity nauseating

Zero gravity

Outside of any significant gravity fields combat can become chaotic, and difficult. Because of the difficulty of building momentum to combat effectively all attacks made in zero gravity suffer disadvantage to hit.


Phlogiston is a turbulent, unstable, multicolored, fluorescent gas-like medium, however it is not a form of matter and cannot be contained physically, even walls of force can only slow down phlogiston and it will shortly flow through and disappear. In phlogiston the very flow of time and space changes and it alters the magical weave so there is very little is known for certain about the Phlogiston.


Phlogiston is extremely volatile, any source of fire will cause phlogiston to erupt into a radiant explosion if there is enough air to allow for combustion. Luckily Phlogiston doesn't mix well with matter, air included, so typically the air envelop of a spelljammer is enough to keep it's crew safe.

An accidental spark near the edge of an air envelope can be enough to burn the whole air envelop of a ship in a second, such explosions deal 8d6 fire damage to everyone and everything within the air envelope, on a successful save damage is halved and the creature will have been lucky enough to have maintained 2d4 rounds of air in a personal air envelope.


Travelers unlucky enough to be stranded in phlogiston soon become calcified after their air envelope goes foul, any creature in phlogiston is affected by a flesh to stone effect after a few hours.

Calcified creatures and organic objects can be restored normally with stone to flesh magic, if they are not lost forever.

Distances in wildspace

Distance in wildspace is relative and hard to measure, but most crews and cartographers have settled upon the SU, a Spelljamming Unit. One SU is the distance that a vessel can travel during one 24 hours while powered by a 1st level spell.


Speed of plot

A ship traveling through wild space or phlogiston is considered to be traveling at thousands of miles per hour. If you are playing a fast and loose campaign, you can consider the vessel to travel as fast as needed for the plot. If you are using a map measuring distances in SU's will let you measure travel easily.


Extended ship rules

These rules extending the UA of Ships and the Sea rules.

Ship Components

A ship is composed of different components:

Hull. A ship’s hull is its basic frame, on which the other components are mounted.

Control. A control component is used to steer a ship.

Movement. A movement component is the element of the ship that enables it to move, such as a set of sails or oars.

Weapons. A ship capable of being used in combat has one or more weapon components, each of which is operated separately.

Armor Class

A component has an Armor Class. Its AC is meant to reflect its size, the materials used to construct it, and any defensive plating or armor used to augment its toughness.

Hit Points

A ship component is destroyed and becomes unusable when it drops to 0 hit points. A ship is wrecked if its hull is destroyed. A ship component does not have Hit Dice.

Damage Threshold

If a ship component has a damage threshold, that threshold appears after its hit points. A component has immunity to all damage unless it takes an amount of damage equal to or greater than its damage threshold, in which case it takes damage as normal. Any damage that fails to meet or exceed the damage threshold is considered superficial and doesn’t reduce the component’s hit points.

Typical Ship Immunities

Ships are usually immune to poison and psychic damage. Ones crafted from metal or stone are also typically immune to necrotic damage. They are also usually immune to the following conditions: blinded, charmed, deafened, exhaustion, frightened, incapacitated, paralyzed, petrified, poisoned, prone, stunned, and unconscious.

(New) Internal Components

Sometimes a component, weapon, or other is located mostly within the ship, and not readily accessible to be attacked from the outside. If attempting to attack such components from outside attacks are made at disadvantage, and any saves are performed with advantage.


(New) Jury-rig

During the heat of combat, repairs are impossible, but skilled bosuns and crew can use an action to make quick preparations and jury rig the ship to grant the ship temporary hit points for one minute.

As an action, a skilled bosun can perform a carpenter's tool or vehicles check with Intelligence DC 15, with advantage if the ship has a full crew, or disadvantage if the crew is at less than half. On a success you give the ship temporary hit points equivalent to 4 times the your relevant tool proficiency and intelligence bonus.

(New) Gravity as a weapon.

It is a known tactic for large ships to perform fly-bys through the gravity fields of smaller ships to cause chaos among the crew of the smaller ships.

When a ship enters the field of a larger ship, or larger body, the ship must immediately make a DC 10 Dexterity saving throw. On a failed save, members of the crew, and other unattended objects fly around causing any further ship, weapons, or officer actions are performed with disadvantage until the end of ship and crew's next turn.

SpellJamming Helms

A Spelljamming Helm is a magical seat or throne designed to magically propel vessels through the sky, wild space, and even phlogiston.

It is said that the original invention of Spelljamming helms is the work of a legendary race called the Reigar. However for centuries now, the art of creating Spelljamming helms has been furthered by powerful archmages and artificers. These days a great variety of helms exist, each unique, and with a "personality" of their own.

Installing a Helm on a Vessel

The actual cost of a helm tends to be compounded by the cost of arcane rituals and labor required to prepare the vessel to work seamlessly with the helm.

To properly and safely install a helm onto a vessel the skilled labor proficient in the Arcana skill, and proficient with one of the following tools: Carpenter's Tools, Tinker's Tools, or Vehicles, any is required. A skilled arcane artisan can finish an installation in a week of work for approximately 5,000 gp in materials and rituals components.

Makeshift installations

It is technically possible to quickly and haphazardly install a helm into place in much less time, and without paying any installation costs. A makeshift installation of this kind can be performed in 10 minutes and by passing an Intelligence (Arcana) check of a DC 15. On a success the helm is precariously installed, on a failed check the helm has not yet been installed yet, and further attempts to quickly install the helm are made at disadvantage.

Until properly installed there is a 50% chance each round that a spell slot used by the helmsman does not take effect immediately, requiring the helmsman to main concentration until the spell takes effect, re-rolling each round, or the spell slot is lost. Additionally, the helmsman has disadvantage on Concentration saves to maintain spells and Constitution saves to avoid Jammer Shocks, described below, while attuned to a helm that has not been properly installed.

Jammed Helms

Occasionally in a crash or other accident a helm becomes jammed, and while attuned to the helm you cannot expend your own spell slots.

Attuning to a Helm

To move a ship with the power of a Spelljamming helm a creature capable of casting spells must attune to the helm. The sensation of being attuned to a typical helm is akin to being immersed in warm water. Although some helms are designed to provide other pleasant and unpleasant sensations.

Jammer Shock

A creature attuned to a helm, can feel the ship. And if the ship is hit by a critical hit, the helmsman must make an Constitution saving throw against a DC 13. On a failed save, a target takes psychic damage equal to half the damage suffered by the ship, and is stunned for a minute. On a successful save, a target takes no damage and isn't stunned.

A stunned target can make an Constitution saving throw at the end of each of its turns. On a successful save, the stunning effect ends.

The Arcane

The trade of Spelljamming Helms is highly regulated by a mysterious race of huge lanky blue giants known as The Arcane. The Arcane seem to have some form of omnisentience, and are capable of just knowing where and when the trade of a helm is taking place, many times arriving just in time, or shortly after, to provide "their services" to register any trades, or "assist" with negotiations, or helm installations. Of course all for nothing more than their just share of the profits.

It must be noted that The Arcane are not a belligerent race, preferring to the Planeshift away at the first sign of violence. However precisely because The Arcane greatly dislike violence, they typically have a number of powerful bodyguards at their service that are more than glad to deal with any rowdy customers. Even if an Arcane is forced to temporarily put negotiations on hold, they will never just let a "customer" go. The Arcane maintain enormous networks of connections, keep detailed ledgers, and have a knack to be there are the right time to close a deal that makes even Devils and Yugoloth jealous.

Moving a Vessel

While attuned to the helm, a vessel has the following movement speeds.

Tactical Movement

  • The helm to propel the vessel through air or space at a speed equal to the highest-level unexpended spell slot × 10.
  • You can use the helm to propel the vessel across or through water and other liquids, if the vessel is capable of aquatic movement, at a maximum speed equal to your highest-level unexpended spell slot x 5.
  • Provided you have at least one unexpended spell slot, you can steer the vessel, albeit in a somewhat clumsy fashion, in much the same way that oars or a rudder can maneuver a seafaring ship.

Overland Travel

When traveling in an atmosphere you may move the vessel at your movement speed in miles per hour.

Wild Space Travel

When traveling through wild space you may move the vessel at extreme speeds which are hard to measure, however a vessel drops out of speed if an object of it's size of larger comes within a few miles, typically at visual distance of it, dropping safely to tactical speeds.

In aflight that does not pass through an asteroid fields or near other astral bodies a ship can travel at one SU per a spell level expended in 24 hours, as long as you can maintain concentration. While maintaining concentration in this way you must pass a Concentration save DC 10 for each hour past the first 8 hours of concentration.


Normally finding a safe route that allows for this sort of fast travel requires good cartographic maps and a character with navigator's tools to spend an hour or so to determine a course. The DC is variant on the local dangers and quality of the tools and maps at hand. Finding a quick route for an escape that will get a ship out of immediate danger normally can be resolved by a skill challenge or 3 successful navigator's tool checks, each requiring a round to complete.

Active Properties

Each helm is a unique, and each has a variety of properties. When creating a helm consider adding a number of the following active properties.

Project Senses. Minor. Whenever you like, you can see what's happening on and around the vessel as though you were standing in a location of your choice aboard it.

Project Voice. Minor. While attuned you can project you voice anywhere, or everywhere, upon the vessel.

Cast Remote Spells. Major. When you cast a spell with a range of touch, you can deliver the spell as if you had cast the spell to anyone aboard the ship. If the spell requires an attack roll, you use your attack modifier for the roll.

Telepathy. Minor. You can communicate telepathically with any one creature capable of speech aboard the vessel.

Telepathy Broadcast. Major. You can communicate telepathically with any number of creatures capable of speech aboard the vessel.

Lesser, ship spellcasting. Minor. While attuned to a helm, you can cast any 3rd level spell, or lower, with a range of self, through the helm, affecting the vessel hooked the to helm instead. However spells that provides you with hit points or temporary hit points, don't provide temporary hit points to the vessel.

Major, Ship spellcasting. Major. While attuned to a helm, you can cast any 5th level spell, or lower, with a range of self, through the helm, affecting the vessel hooked the to helm instead. However spells that provides you with hit points or temporary hit points, don't provide temporary hit points to the vessel.

Supreme, Ship spellcasting. Major. While attuned to a helm, you can cast any 7th level spell, or lower, with a range of self, through the helm, affecting the vessel hooked the to helm instead. However spells that provides you with hit points or temporary hit points, don't provide temporary hit points to the vessel.

Embedded Spells. Minor. Many helms have a number of spells that can be cast by any caster that is attuned to the helm.

Series Helms. Minor. You can link several of these helms together, the highest unused spell slot of any of the helmsmen is used to determine the base movement capabilities of the ship.

Life-Jammer Helm. Minor. Instead of spell slots, the ship can be powered with life force in place, or in addition to spells. Powering a ship in this way deals 1d10 hit points per equivalent spell level used. The max spell level you can emulated is equivalent to one third of your level rounded up. These helms tend to feel extremely unsettling and cold, anyone familiar with spelljamming can easily recognize a life jamming helm.

Types of helms

Most helms are unique but can be divided into the following power categories.

Rarity Vessel
Minor Properties Major Properties
Lesser Rare 25 t 1 - 2 -
Minor Very Rare 100 t 2 - 3 -
Major Legendary 250 t 2 - 3 1
Master Artifact N/A 2 - 3 2

Non-traditional Helmsmen

The rules for controlling a spelljamming helm assumes a traditional spellcasting character class such as a wizard or cleric, but there are other options for classes, some presented here.


Barbarians would not seem like a good fit for a helmsman, however they make excellent Life-Jammer helmsmen thanks to their endurance. While raging a barbarian can benefit, and maintain, the benefits of a Life-Jammer reducing any damage in half, and they have advantage on saves against becoming jammer-shocked.


Druids cannot typically cast spells while wild shaping, however they can still power a helm while wild shaped.


Monks can use ki to power Life-Jammer helms, but there are also some helms that have been reconfigured by artificers of cultures such as Wa from Realm Space to be powered directly with ki.

Ki Points
Spell Level
1st-4th 2 1st
5th-8th 3 2nd
9th-12th 4 3rd
13th-16th 5 4th
17th-20th 6 5th
Paladins, and other innate Healers

Paladins and some other classes like Celestial warlocks, Divine Soul sorcerers, and Circle of Dreams druids have access to magical healing powers, that exist independent of spell slots. These magical energies are very specifically attuned to life giving energies, and cannot be converted directly into the raw magical energies required to power a regular Spelljamming helms. These energies can be used to feed a Life-Jammer Helm, 5 lay on hand hit points, or one healing die, can be used to ignore ond d10 worth of damage when powering a Life-Jammer.


Arcane tricksters are an obvious choice for a rogue helmsman, however the Thief rogue deserves special mention, because at 13th level they gain the Use Magic Device feature, which can be used to basically power a helm without any inherent spell casting abilities. For the sole purpose of powering a Spelljamming helm a Thief rogue is considered to have the spellcasting abilities of a warlock of half their level.


Sorcerers have sorcery points which can be converted into spell slots to power a helm, but they can also be used directly to power a helm at the conversion rate shown in the Players Handbook without requiring an additional bonus action.


Warlocks have limited spell slots and regain slots on short rests. Luckily for them it is possible to benefit from short rests while controlling a helm when as long as they are not under the duress of combat or traveling through especially dangerous space like an asteroid field.

Brewed by Jay, a.k.a. u/KameBit and @KameBit

Find more brews and ideas at KameGames.com

The rules presented here are built upon what we know about Spelljamming helms from the Dungeon of the Mad Mage and the Unearthed Arcana Of Ships and the Sea

Special Thanks to my fellow brewers of the Discord of Many Things

Art Credits: Arcane art from TSR's Monstrous Compendium, Planescape, Appendix II.
Other art is from Treasure Planet from Walt Disney Pictures