This is a synopsis of the book and scrolls found in the Phaerimm den (as translated by Oswald)
Game Setting Background
Imagine a universe where square worlds spin around gemstone suns. Where planets lie cradled in the roots of an oak tree so vast its leaves twirl around brightly burning suns. Where ships of wood sail the void between worlds, and battle each other with catapult and ballista, spell and sword. Where an asteroid may be a safe harbor, a slaver’s den, or a hungry creature eager to devour any that pass by. Where daring swashbucklers and scoundrels race for fantastic treasures and literally touch the stars. Where terrifying beasts with the power to destroy whole worlds roam.
Welcome . . . to the universe of Spelljammer!
In the Spelljammer campaign, the fantastic is possible and one is limited only by the depths of their imagination. Sailing ships, enwrapped in bubbles of air, travel empty Wildspace, moved by the power of their mystic helms. Gravity is a matter of convenience, where a captain can tour the bottom of his ship, and worlds come in all shapes and sizes. Whole solar systems are surrounded by colossal spheres made of an unbreakable, crystal-like substance to protect them from an ocean of swirling light and color, the flammable Phlogiston, which divides the void between stars.
Worlds in SJ are typically planets which are part of larger systems called “spheres”. Sphere systems are literally surrounded by unimaginably huge spheres made up of an unknown material which seems indestructible (called “Crystal Spheres”). These spheres in turn bob about in a substance called Phlogiston, or the Flow, which is incredibly flammable but seems to be incapable of existing within a sphere. Otherwise it is undetectable except for the brilliant, chaotic collors it is composed of. It is odorless and seems to have no effect on breathing. In the Flow planar contact of any sort is impossible, even for the gods/powers.
Physics operate differently in the SJ universe. Gravity is a constant earth-normal powered force. Every object exerts this, but the direction alters according to shape, and only objects of a certain size (generally about 25’ long) exert enough force for a gravity plane to develop. Spherical objects attract objects towards their surfaces uniformly, much as gravity works in our own universe. Objects with a more irregular shape develop a gravitational “plane” which extends along the most convenient axis, generally the longest. This plane works in both direction so that it is possible, for instance, to walk on the bottom of a ship.
Gravity planes exert a slight outward force, so that an object dropped overboard will osscilate across the plane until it settles there, and will then drift slowly outwards from the ship to be eventually expel from the air envelope.
This gravitational plane exerts a “field” which extends to the limit of a body’s air envelope. When two such fields come into conflict the gravitational field of the larger body dominates. This makes it dangerous to be out of pitch or alignment with a larger ship if you enter its gravitational field/air envelope. Specifically, this means that when a ‘jammer enters a planetary atmosphere the planet’s gravity becomes dominant. (You can walk on the bottom of your ship in space, but in a planet’s atmosphere you would fall off and land on your head.)
Also, though gravity fields only extend to the edge of the air envelope anything larger then 10 SJ tons in size produces a gravity “well” which extends 12,500 yards (at least; some planets have larger wells) out from that body. For those knowledgeable about these wells (and using a proper craft) one can “sail” or “ride” these wells much like a sailing craft uses the wind. This movement is always tactical and thus only practical for movement in dense astroid fields and similar locations.
The more common manifestation of these wells is the way they pull vessels out of spelljamming speeds when entered. Within these wells ships shift instantly to tactical movement. This shift is obvious to the crew as a lurching sensation but causes no damage.
All objects drag air with them whenever they leave an air envelope [note, however, that unless an object leaves an air envelope the air tends to stay stuck to the ship. This tendancy is forceful enough for the air to avoid slowly drifting out at the gravity plane like a solid object). A typical human, for example, will drag enough fresh air with him/her to breathe for 2-20 turns. After that time runs out the air will turn foul for a like period of time and then become deadly and unbreathable.
For each SJ ton of size a ship drags enough air to support one man sized creature for 4 months. So, a hammership (60 tons) can support 60 crew for four months without needing to refresh the air. If the ship had 120 crew it could only last 2 months. When a vessel reaches its air limit the air becomes fouled; it smells bad and is stale and humid. All attacks and proficiency checks in a fouled atmosphere are at a -2 penalty. Air remains fouled for the same amount of time it remained fresh, once that time wears out it becomes deadly; each turn everyone aboard must save versus poison or pass out. If unconcious each turn they must save versus poison or die.
While important air is relatively easy to replenish, entering a larger air envelope, like that of a planet or astroid is one of the most popular and cheapest methods. Some spells, like Wall of Fog or Obscurement can also replenish the atmosphere. There are many magical items which also affect air use. Green plants will refresh air, some vessels make great use of these for just this purpose. Many astroid colonies keep at least half their surface area reserved for plants for this reason as well.
Spelljmming is the province of the helmsman, the individual who sits on the helm and directs the ship’s general motion (sails, rigging, and crew provide fine maneuvering). In most cases this is a spellcaster of sorts, but there are a handful of helms which allow nonspellcasters to fill this role.
When spelljamming the helmsman in a sense merges with the ship, he/she feels as if the are personally flying through space, and can percieve the world around the ship as if he were standing on the aft deck. The helmsman perceives damage to the ship as white flashes of pain, but takes no actual, personal damage in most cases. Sometimes, however, the pain is intense enough to cause unconciousness; this is called “spelljammer shock” and is usually a result of a critical hit.
In many ways, helming a vessel is instinctual, because the helmsman feels he/she “merges” with the vessel he/she can generally control the vessel as easily as walking. It’s possible, with training and practice of course to become much better (the Spelljamming non-weapon proficiency) but any helmsman can handle most functions. It’s important to keep in mind, however, that the only time the helmsman controls maneuver on a vessel is when the mininmum crew is listed as 1 (there are few such vessels). Usually, the sailhands control all of the finer aspects of maneuveur, the more skilled they are the better the craft handles.
While spelljaming the helmsman retains his/her normal senses and can hold a conversation with those nearby. In general, spelljamming is no more difficult then walking (except during combat) so that anything a person can reasonably be expected to concentrate on while walking can be done while ’jamming.
Helms are the primary method of powering spelljamming vessels. Simply put, a helm is a magical device which channels magical energy from a some source into motive force for the ship it’s attached to. Some helms operate on slightly different principles but these are few and rarely seen in the Known Spheres.
There are several different types of helms of varying types and abilities. I list the types most common within the Known spheres below, and the “standard cost” for such a helm in an active spelljammer port like the Rock of Bral or Refuge. Note that in other places the price quickly becomes what the market will bear and thus can drop or rise considerably. Most common are Major and Minor Helms
Here are the common ship officers:
- First Officer (First Mate)
- Ship’s Mage
- Ship’s Cleric
- Ship’s Spellmaster
- Quartermaster (responsible for supplies, crew, etc)
- Tactical Officer
- Security Officer
- Intelligence Officer