Spelljammer-Adventures In Realm Space
The largest creatures in the Known Worlds are larger than the planets themselves-in fact, they often carry planets on their backs. They are given the collective name of starbeasts, though they may appear as monsters, humanoids or gods.
Starbeasts are usually unique beings (in the sense that titans are unique) found in crystal spheres which support celestial bodies. Not all spheres use starbeasts to support the planets within, however.
Starbeasts are living things. They move, and in some cases have sentience and can react to others. They are normally 1-4 mllion miles tall, and in large spheres a number of them must stand atop one another in order to reach the bottom of the sphere (for example, the world is held by a giant on the backs of four elephants, wich in turn rest on a huge turtle, which moves about at the bottom of the crystal shell).
The starbeasts are similar to the crystal shell, and share that material’s strange ability in that they have neither a gravity nor an atmosphere, which should accompany creatures so large. Why these objects have neitehr is a mystery. Sages mumble something about the “will of the gods” and change the subject.
It is possible to moor a ship alongside a starbeast but, since no gravity, actually walking on one is very difficult (some would say pointless). Communication is extremely difficult, given the difference in scale. Some have been known to pass on messages or answer questions. Some are known in their systems as oracles, some as gods, and some as servants of (or those being punished by) the gods.
Where a world is in contact with a starbeast, the land is usually a blasted area in perpetual shadow. The land itself is twisted by the continual pressure of the creature’s fingers or back or flippers. Nothing grows on the side of a starbeast, even in those parts within the atmosphere of the planet.
Starbeasts cannot be harmed by any spells or spell-like effects, again, a similarity with the crystal shells. They are unaffected by weapon attacks (or are so large that the attacks inflict no more damage than a gnat bite to a fully armored warrior) and any damage inflicted on them heals almost immediately. Creatures of gargantuan size might gain their attention.
It is not possible to slay starbeasts by conventional means, and the effects should one be slain are horrible to contemplate. Legends tell of great heroes or villains who have tried to slay these creatures, only to destroy their own world in the process, or become enlarged and replace the slain starbeast in the sky.
Natives of planets carried by starbeasts insist that starbeasts are the only method of planetary movement. They say that all other planets are carried by starbeasts as well, ones which are invisible and intangible becuase those who live on those planets are not worthy of the starbeast’s notice.