Overview alt (Spelljammer Supplement)

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Spelljamming helms

Spelljamming helms are the central setting concept which allow interplanetary and interstellar space travel for vessels which would otherwise not be spaceworthy, in the form of a helm (as in rudder, not armored helmet). Any spellcaster may sit on a spelljammer helm to move the ship. The mysterious race known as the Arcane is the sole manufacturer and distributor of spelljamming helms. They are a method of converting magical energy into motive power.

Gravity and Air

All bodies of a sufficiently large size have gravity. This gravity usually (but not always) exerts a force equal to the standard gravitational attraction on the surface of an Earth-sized planetary body. Gravity in the Spelljammer universe is also an exceptionally convenient force, and almost always works such that "down" orients itself in a manner most humanoids would find sensible.

All bodies of any size carry with them an envelope of air whenever they leave the surface of a planet or other stellar object. Unlike real-world astrophysics, this air envelope is not dispersed by the vacuum of space. These bubbles of air provide breathable atmosphere for varying lengths of time, but 4 months is considered "standard".

Crystal Spheres

A crystal sphere (also known as a crystal shell) is a gigantic spherical shell which contains an entire planetary system. Each sphere varies in size but typically they are twice the diameter of the orbit of the planet that is farthest from the sun or planet at the center of the sphere (the system's primary).

The surface of the sphere is called the "sphere wall" and separates the void of "wildspace" (within the sphere) from the "phlogiston" (that surrounds and flows outside the sphere). The sphere wall has no gravity and appears to be impossible to damage by any normal or magical means. Openings in the sphere wall called "portals" allow spelljamming ships or wildspace creatures to pass through and enter or exit from a crystal sphere. Portals can spontaneously open and close anywhere on the sphere wall. Magical spells (or magical items that reproduce their effects) can allow a portal to be located. Other magic can open a new portal or collapse an existing one. Ships or creatures passing through a portal when it closes may be cut in two.

Wildspace

Wildspace is similar to the outer space of science fiction, with planets, asteroids and stars, but with different physics. Gravity is either none or the same as that of Earth, and is directed towards the center of planet-sized bodies; on large objects in space like spacecraft and enormous creatures gravity is directed towards a flat plane running through the object's long axis, allowing characters to stand on the decks of ships.

The Phlogiston

The phlogiston is essentially a big ocean of a unique element that is neither air, fire, water, or earth. The phlogiston (also known as "the Flow") is a bright, extremely combustible gas-like medium that exists between the Crystal Spheres. A signature property of the substance is that it does not exist within the boundaries of a crystal sphere, to the degree that it cannot be brought into a crystal sphere by any known means up to and including the direct will of deities. Every crystal sphere floats in the phlogiston, very slowly bobbing up and down over time. Travel between Crystal Spheres is facilitated by the formation of "Flow rivers" – sections of the phlogiston which have a current and greatly reduce travel time. Travel through the "slow flow" (i.e. off the Flow rivers) is possible, but very dangerous.

The Spelljammer

The Spelljammer is a legendary ship which looks like a gigantic manta ray, and houses an entire city on its back. All spacefarers (people who live in wildspace) have heard of the Spelljammer but very few have ever seen it themselves. It is this ship that gives its name to "spelljamming", "spelljamming helms" and anything else connected with spelljamming. The ship has been reported to have been seen in countless spheres for as long as records go back. Even some groundlings (people who live on planets that have very little or no commerce with spelljamming communities) have legends about it. There are hundreds of conflicting legends about this ship, and a mythology has developed about the ship that is similar to the legends surrounding The Flying Dutchman.

As a living thing (although it does not consume any matter, it does absorb heat and light through its ventral (or under) side and uses them to produce air and food for its inhabitants), the Spelljammer has a complex life cycle and means of procreation. Normally the ship has no captain and wanders the cosmos seemingly aimlessly. When the Spelljammer has a captain, obtained through another complex process, it will create Smalljammers (miniature versions of the Spelljammer) that go forth as its spawn. Apparently there can only be one Spelljammer at any one time. One Smalljammer will mature into a full Spelljammer ship if its predecessor is ever destroyed.

Races

Alien races inhabiting the Spelljammer universe included humans, dwarves, xenophobic beholders, rapacious neogi, militant giff (humanoid hippopotami), centaurlike dracons, hubristic elf armadas, spacefaring orcs called "scro", mysterious arcane, the Thri-kreen insectoids, bumbling tinker gnomes, mercantile illithids and simian Hadozee.