Spelljammer

Spelljammer is a fictional setting used by the Dungeons & Dragons role-playing game. It introduces the concept of crystal spheres (roughly the size of a solar system), which may contain mutliple worlds and are navigable using spelljamming ships (as the name implies, operated by the power of magic). Both space and alien planets are inhabited by strange and dangerous creatures unknown to material primes, and the alien races engage in spelljamming and space warfare as well.

The setting is designed to allow some fantastic space adventures to take place within the traditional swords'n'sorcery universe of Dungeons and Dragons. With their own magical gravity and atmosphere envelope, the "ships" involved tend not to resemble the spaceships of science fiction, but galleons, animals, or even more wildly fantastic shapes. Some of the ideas owe much to the fiction of Jules Verne and his contemporaries, and to related games and fiction with a steampunk flavor.