Go big or go home.
The rogue planet called [Insert Impressive Name Here] has been floating in the Dark Tapestry for untold epochs. (A rogue planet is a celestial body that orbits no star)
This rogue planet is found to one living creature that considers itself a deity. To feed the rogue planet smashes into other celestial bodies, breaking them apart, making it easy for digestion.
Said rogue planet targets the Golarion system. Can add drama by making it a servant of Rovagug searching for its former master. Due to The Gap no one knows where to his former master is located now.
Heroes must search for a way to stopping this rogue planet god from devouring and destroying the planets of Golarion in a rage once it realizes Rovagug is gone.
One possible path? The heroes must find ancient weapons that were once used to throw down Rovagug by the gods that were actual spaceships used by mortals to aid their deities in the fight. The heroes must find one of these 'swordships' to pierce the rogue planet god's heart and slay the soul inside.