Spelljammer 101: The basics of Spelljammer

Ad astra per aspera

("To the stars through hardships")

— Latin proverb

Way back in 2nd edition of Dungeons and Dragons, the management philosophy was to crank out as many settings as possible to appeal to as large of an audience as possible. Since Sci-fi was popular at the time, the development team was forced to create a space setting.

And oh boy, did they.

Throwing in a mishmash of tropes, turning some on their head, and creating entirely new ones, Spelljammer was born.

Of course, the very management that demanded it also hated it, so each one of it’s supplements only got a single printing, leaving it to fade into obscurity. But no longer! Here, I intend to explain the basic ideas and rules of the Spelljammer setting, so that people can better understand the strange ways space travel works in D&D. With the exception of how physics work, most of these have a “usually” in them, as Spelljammer is designed to defy expectations.

Part 1: Spelljammer, spelljammers, spelljamming, and the Spelljammer.

First thing first: Spelljammer is not sci-fi. This is more of a pet peeve of mine than anything else. I’ve taken to describing it as “medieval space fantasy” because people have a hard time separating “in space” from science fiction. People are not in rockets or your typical spaceships/starships: They are on sailing ships. With sails, rigging, etc..

Sorry, I had to get that out of the way.

Sailing ships. Well, for the most part. There are several spelljamming ships that aren’t sailing ships, and most of them are certainly not NORMAL sailing ships that would be seen on our world. Spelljamming ships are usually wooden vehicles, sometimes with metal plating, almost always armed with canons, ballistae, catapults, and other weapons that fit in with D&D. This is getting kind of rambling, but point has been made, moving on.

The secret to how spelljamming ships fly is a magical device known as a helm. The helm is a chair or throne that is bolted to the floor on a ship, when a magic user touches the chair, their magic is used to power it, and they can cause the ship to rise into the air. In addition to the ability to fly a ship, the helm also gives it’s user awareness of the area around the ship, to help with maneuvering and allowing them to be safely below deck and not exposed on the deck of the ship.

Of special note, is that while “a spelljammer” can refer to the ship, one of the crew, or the magic user manning the helm, “the Spelljammer” is the name of the legendary living ship with a whole city on it, from which the setting gets its name.

Part 2: Everything you know about space is wrong.

Well, not everything. The space between planets is still an airless void, referred to as “wildspace”, and most things usually orbit around other things. The first things that someone would notice when leaving a planet’s atmosphere are air envelopes and the way gravity works.

Air envelopes

When a object or creature leaves the atmosphere, it takes with it a bubble of air relative to it’s size. A human sized creature takes with it enough air to last them anywhere from 40 minutes to 6 hours (I couldn’t tell you why it varies that much), and a large object, such as a ship, can take enough air for a crew to breath fresh air for months. After a time, the air envelope loses it’s freshness and becomes fouled, and people breathing fouled air take a penalty to checks. After the same amount of time to become fouled passes again, the air becomes poisonous and will eventually kill anyone who tries to breath it.

Coming into contact with the atmosphere of a planet with clean air will completely refresh a ship’s air envelope, or coming into contact with another ship’s envelope will cause an exchange of air, equalizing the freshness of both, according to the envelopes’ sizes.

Gravity in wildspace

After leaving a planet’s gravity, you would think that you would start floating off into space, right? That isn’t the case in Spelljammer, instead it follows a few rules:

1. Gravity’s range is determined by the size of the planet, creature, or object. A larger planet's gravity can extend out for miles, while a human's would only extend out a couple of feet.
2. Gravity is constant. There are always a few exceptions, but gravity is usually equal to our earth’s gravity whether you are on a planet (regardless of size), a moon, or a ship.
3. Down is subjective. On a planet or mostly spherical objects in space, down is towards the center. On a less spherical shaped object, like a ship, the gravity is usually divided by a plane. The top deck of a ship and usually the first deck are gravitationally aligned one direction, but further decks and the bottom of the ship are aligned the opposite direction. Once again, there are exceptions to this rule, a hallow moon could have you walking on the outside of it, then you enter a cave and you find the center of that moon is "up".
4. Gravity is determined by the largest object. Near a planet, that planet’s gravity takes over. Near a larger ship, that ship’s gravity takes over. This even applies to a person, who, if they were to drift away from their ship, could put objects or even smaller creatures into orbit around themselves.

Part 3: The wonders of wildspace

Once you have your bearings in wildspace, you would get a chance to look around at the wonders of your sphere, the immensely enormous sphere of an unknown substance that contains the sun, planets, asteroids, and everything else that exists in wildspace. Most spheres have a “primary”, or the body that is at the center that most things orbit around, which is most often a sun, but exceptions do exist.


The first thing you might notice about a sun, planet, moon, etc. is its shape. Spherical worlds are common, but far from the only shape that worlds can be. Some are coin shaped, some are geometric shapes, some are just weirdly amorphous. Just about any shape is possible (and likely exists somewhere).

In addition to it’s shape, planets, moons, and other bodies in wildspace are categorized by what element they are largely made of:

• Fire worlds are balls of flame, uninhabitable to most beings, and typically act as suns to illuminate everything in the sphere. Strangely, many are simply named “the Sun”.
• Earth worlds are largely made of earth, or at least have a decent amount of landmass on the surface. Many inhabited worlds are earth worlds, though not all are inhabitable.
• Water worlds are huge bodies of water sometimes with islands dotting the surface, and sometimes not. In colder spheres, water worlds can be entirely frozen.
• Air worlds are giant orbs of air, sometimes with floating islands inside. Unless the air is fouled, they are good places to refresh a ship’s air envelope.
• Living worlds are a type of world that is largely living matter, usually plants, and is very rare. This can range from a “relatively” small one that has grasped onto several moon sized worlds, or an enormous tree that fills it’s sphere and holds entire worlds in it’s branches.

There are also rare elemental mix worlds, but that’s a bit complicated for this guide, so maybe I will go into that if I make a more advanced guide in the future.

Finally, there are the stars. Which… are not stars as we know them. They could be glowing gems, portals to the plane of radiance, or they could simply be portals out of the sphere. Once again, anything you could think of could be the case somewhere.

Except for them being distant suns, billions of light years away. Because that would be weird.

Part 4: Beyond the crystal sphere

What do you do when the worlds of your sphere no longer interest you? When you need further adventure? When you need to REALLY get out of town?

You can head to another crystal sphere, that’s what.

As far as the furthest world is from the primary, and that far again, is the crystal sphere. It is mind mindbogglingly huge, to the point that if you go up and touch it, it will seem absolutely flat, despite being round. Most spheres have naturally occurring portals out of it, some are consistently open, others open and close on some schedule or randomly. Prepared travelers will have magic that allows them to temporarily open a portal themselves.

Once you make it through a portal, you will be bombarded with a brilliant display of a multicolored substance known as the phlogiston. It is what surrounds the spheres and flows between them, allowing travel. You can use these flows between the spheres to travel anywhere you desire. It can take months, and you may need to make stops at spheres along your way to freshen your air envelope and supplies.


Things to note about travel in the phlogiston:

1. The phlogiston mixes with the air envelope of the ship, and while it does not affect the air quality at all, it is extremely flammable and is very dangerous to anyone starting a fire or using fire magic.
2. The phlogiston cannot enter a sphere, no matter how hard you try.
3. While in the phlogiston, it is not possible to use any extraplanar magic- You are unable to summon creatures, use spells like Mordenkainen’s Magnificent Mansion, or items like bags of holding or portable holes. Similarly, clerics are unable to communicate with their deity.

Part 5: Other crystal spheres

After traveling through the phlogiston, you will eventually (hopefully) reach another crystal sphere. Once a portal is found or created, your ship can enter to explore the new worlds available to you. Things may be similar or completely different from your home sphere. In addition to unusual worlds, the rules may be different. Gun powder/smoke powder may not work, or certain races may feel an unwelcoming feeling of foreboding that manifests (mechanically) as a penalty to rolls, preventing them from having a major presence in a sphere.

In addition to the main three D&D settings (Realmspace, Greyspace, and Krynnspace), there are literally infinite spheres to explore, and mix that with planar travel and there is no end to the adventures that adventurers can go on. Some spheres aren’t easily traveled to (the spheres of the Eberron and Dark Sun settings), but a DM can always add those in their game if they want.



I hope that you enjoyed my guide, and that you learned a lot about the Spelljammer setting! In the near future, I plan to add more posts about it, including an examination of the setting’s special rules as they would fit into 5e, how I will codify those rules, a write up of the adventure I’ve made for my players (leading to an old module that I’m going to adapt for the next part of their journey), and more posts about the basics of Spelljammer (I’m thinking “Spelljammer 102: Peoples of wildspace”).


See you next time, space cowboy wizard.