Some spitballing from a chat session in #ENWorld (as memory serves):
Stars are a large-scale connection to the divine essence of the universe. Almost untouchable by the humanoid races. Bits of star-like matter (a nice divine unobtainium) fall from the heavens from time to time, infusing those who grab them with the very power of the gods. These mere mortals ascend to a place in their own lands and the universe itself; they crave more of the materials, but stars are separate for a reason. Get these bits of matter too close to any other piece and they tear apart the very fabric of the planes, creating nasty singularities.
The hunger of the Lords who possess the material create major wars between planets and planes; those who can travel the stars send their elite 'priests' (who have been invested with a portion of the will of their 'Creator') to do battle and retrieve sympathetic pieces which will combine with their own power in a way which is more stable.
The stars, which are to be the only source of this power, produce armies of Inevitable-like creatures to hunt the Lords. From their heavily warded palaces on hidden planes and planets the Lords fight each other and the heavens themselves through proxy, sometimes laying wastes to entire layers of the planes to protect their investments.
Hey... someone asked for a better version of Spelljammer and this is what they got
Slainte,
-Loonook.
Stars are a large-scale connection to the divine essence of the universe. Almost untouchable by the humanoid races. Bits of star-like matter (a nice divine unobtainium) fall from the heavens from time to time, infusing those who grab them with the very power of the gods. These mere mortals ascend to a place in their own lands and the universe itself; they crave more of the materials, but stars are separate for a reason. Get these bits of matter too close to any other piece and they tear apart the very fabric of the planes, creating nasty singularities.
The hunger of the Lords who possess the material create major wars between planets and planes; those who can travel the stars send their elite 'priests' (who have been invested with a portion of the will of their 'Creator') to do battle and retrieve sympathetic pieces which will combine with their own power in a way which is more stable.
The stars, which are to be the only source of this power, produce armies of Inevitable-like creatures to hunt the Lords. From their heavily warded palaces on hidden planes and planets the Lords fight each other and the heavens themselves through proxy, sometimes laying wastes to entire layers of the planes to protect their investments.
Hey... someone asked for a better version of Spelljammer and this is what they got

Slainte,
-Loonook.