Portals can spontaneously open and close anywhere on the sphere wall.
Openings in the sphere wall called "portals" allow spelljamming ships or wildspace creatures to pass through and enter or exit from a crystal sphere. The sphere wall has no gravity and appears to be impossible to damage by any normal or magical means. 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). 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). These bubbles of air provide breathable atmosphere for varying lengths of time, but 3 months is considered "standard".Ī crystal sphere (also known as a crystal shell) is a gigantic spherical shell which contains an entire planetary system. Unlike real-world astrophysics, this air envelope is not dispersed by the vacuum of space. 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.Īll bodies of any size carry with them an envelope of air whenever they leave the surface of a planet or other stellar object. This gravity usually (but not always) exerts a force equal to the standard gravitational attraction on the surface of an Earth-sized planetary body. Within the Dungeons & Dragons universe, they are a method of converting magical energy into motive power.Īll bodies of a sufficiently large size have gravity. The mysterious race known as the Arcane is the sole manufacturer and distributor of spelljamming helms. Any spellcaster may sit on a spelljammer helm to move the ship. 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. 2.1 Advanced Dungeons & Dragons (2nd edition).A strong Age of Sail flavor is also present. Though the cosmology is derived largely from the Ptolemaic system of astronomy, many of the ideas owe much to the works of Jules Verne and his contemporaries, and to related games and fiction with a steampunk or planetary romance flavor. However, unlike Planescape it keeps all of the action on the Prime Material Plane and uses the crystal spheres, and the "phlogiston" between them, to form natural barriers between otherwise incompatible settings. Like the Planescape setting, Spelljammer unifies most of the other AD&D settings and provides a canonical method for allowing characters from one setting (such as Dragonlance) to travel to another (such as the Forgotten Realms). Flying ships travel through the vast expanses of interplanetary space, visiting moons and planets and other stellar objects. The Spelljammer setting is designed to allow the usual sword and sorcery adventures of Dungeons & Dragons to take place within the framework of outer space tropes. With their own fields of gravity and atmosphere, the ships have open decks and tend not to resemble the spaceships of science fiction, but instead look more like galleons, animals, birds, fish or even more wildly fantastic shapes. Ships powered by spelljamming helms are capable of flying into not only the sky but into space. Crystal spheres may contain multiple worlds and are navigable using ships equipped with "spelljamming helms".
Spelljammer introduced into the AD&D universe a comprehensive system of fantasy astrophysics, including the Ptolemaic concept of crystal spheres. Spelljammer is a campaign setting for the Advanced Dungeons & Dragons (2nd edition) role-playing game, which features a fantastic (as opposed to scientific) outer space environment.