A basic story for an adventure, still quite bare bones to leave plenty of room for customisation and creativity based on your own groups desires and levels.
Scene one, Star fall: High above Etape three white hot spots of light approach the planet at a low angle, as they approach the night side of the planet their brilliance lights the sleeping towns and cities as the noonday sun. The streak across the sky low and fast with a trail of fire and shockwave that shakes the earth in its passing. Everyone with any kind of magical potential instantly feels their enormous arcane power. Somewhere a reasonable distance from your adventures each makes impact with a flash of blinding light and a shudder that breaks glass and dislodges roof tiles. If there are no magical members of the party an NPC should be seen to point out the fact the star had incredible power. As the players leave the starting settlement they should observe cloaked riders leaving in the same direction at high speed just ahead of them.
The three sections can be done in any order. At all three sections they should come across the cloaked figures who are revelled to be a cult who worships dark stars and aims to corrupt the star's pieces. Upon reaching the first of the sites they should be informed that the objects are in fact a fallen star who's heart stone shattered into three. While in three the star's heart is susceptible to corruption or destruction however should the pieces be reunited they would return to their true form of the star dragon and leave with the pieces of star which it would reform and return with to the sky. At the second site the starlings will be reluctant to give up the piece of the star questioning your motives. You will meet a powerful wizard who aims to use the pieces of the star's heart and other star gems to create powerful magical items to feed his power. The final piece of the star should already be partly corrupted and the players should have to find a way to remove the corruption if they can. They should be presented with multiple options such as the working with the wizard to take the star apart and use its power, trying to get the cult to remove the corruption by force of negotiation or they can try to bring the fourth piece of the star down from space and hope its power will be able to cleans the corrupted piece. You can use this in earlier star sites as a failure state if the players do poorly against the cultists.
The sunken star: A piece of the star landed deep out to sea. As the players approach the shore closest to the impact they should find a significant amount of destruction due to a Tsunami created by fall. The players will struggle to find passage out to the star and may need to do various side quests and minor steps along the way in an attempt to get out there. The players should be encouraged to think of their own way of getting out to the star piece but some options could include building your own vessel, asking Mer-people for help or attempting to infiltrate another faction going after the star's vessel and seizing control of the ship when they reach their destination. On reaching the spot the players will see that created out of a silvery white material a small underwater settlement has developed with tall spires reaching out to the surface. Starlings (a humanoid being created by the star) will serve as NPCs and potentially enemies along with the ever present cultists. There are also multiple options for various other threats like local pirates or sea life coming into conflict with the Starlings.
The silver crown: High atop a tall mountain the star came to rest shattering the peak of the mountain, while many of the shards have fallen to the surface littering the ground bellow some appear to have been frozen in time midway through breaking creating a hallow of broken rock surrounding the mountain top. They may find thin bridges made of floating rubble like stones in a river and near the sight bridges made of the silver material with a silver fortress at the star. Encourage the players to interact with NPCs and find creative way to overcome obstacles and bridge gaps you can create as they make their way up the mountain and through the rocky shards. Along with the cultists and starlings additional problems need to be dealt with as various dragons and roc have been attracted by the magical energies and are locked in battle for the skies surrounding the new landscape. Dwarfs living in the base of the mountain have also begun to make the occasional fortress inside the floating chunks of rock from which to assault starlings as the star shattered their sacred mountain home .
The light in darkness. On the surface the players find a massive crater with a pool of cooling semi molten rock at the bottom. The star appears to have melted its way into the earth but the blast opened up passage ways into the tunnels and caves that reach deep into the earth. On reaching the star piece the players will find it in a vast cavern filled with life that was used to scraping out an existence from the scrapes of energy that trickle down from the surface and that are provided by magical and volcanic materials. Now bathed in huge amounts of heat and light the local ecosystem is on over drive colonising the place which has attracted an array of creatures out of the depths for the players to deal with. Once again the starlings have made a small silver town but their star burns hot creating areas of danger throughout the area and even areas of molten rock melted by unpredictable fluctuations and beams of light that the star undergoes. It isn't recommended that this is the first site.
I encourage you to be very flexible with these ideas and invent and remove what ever is most suitable.