Dont forget…. While the campaigns and stories you tell now tell their own stories…. Introduce obscure lore that hints at the final story arch that wont be realized until a multitude of campaigns have played out.

As future campaigns move forward drop more hints and clues, not to give the story at this point, but to have a trail people can follow back later, amd be surprised that it wasnt noticed already when the final arch is revealed.

That the giant space-born celestial being that was cacooned within the planet was disturbed when a large chunk of it was blasted into space, startimg a series of escalating events that culminate in the race to stop the emergence that would destroy everything in the starsystem this world exists within.