Let me explain. Twenty years ago, this world was safe and prosperous. There was a great trading alliance of dozens of tribes, each with their own lift-fruit groves that kept their islands safe and their ships aloft. There were many great clans - the Vixens, the Talons, the Nightfallen, the Firebearers, the Sweethearts, the Mothwinged - and they all lived in harmony. This was the heart of their alliance, a great island where they came to trade, to give thanks to the gods, and to undertake the building of new ships and the raising of new islands.
But then the plague came. A cursed blight, withering the hearts of the Sweethearts and spreading to the liftfruit groves. They fought, valiantly, but islands and ships began to fall from the sky as the liftfruits at their core became too corrupt and lifeless to support their charges. The people of the alliance began to withdraw, setting in place quarantines and banning any non-essential trade, yet still the plague spread. The clans became paranoid, blamed each other for the unnatural spread of the plague, and trade withered still further - and with it the supply of foreign lift-fruit to those tribes that depended on them to keep themselves above the poisonous fog of the land below. Some perished. Some planted their own liftfruit groves and withdrew. A few who still believed in the alliance sought desperately for a cure to the corruption - a cure that lives, now, in a single grove of liftfruit on this island that are free of the taint, their mana modified to withstand the corruption.
That grove of liftfruit, though, was not yet mature when very little was left to keep this island safe. The people who lived here - the Last Vow of Sisterhood - took the last few wholesome fruits they could spare to power their ships and fled with a few immature fruit to continue their work from, as this island was believed to no longer have the strength to remain in the air. They took the knowledge of the cure's propogation with them: I know not where. All communication between isles had been lost by the time that that desperate extreme was reached.
But the few remaining liftfruit on the isle, the blessed ones, were just enough extra buoyancy that this isle has survived the loss of its people. I used the last of the strength of the central liftfruit on a desperate gamble - to call people from another world to save this place, in the hopes that they would discover the now-ripe grove and replace the heart of the isle before it gave way.
That gamble has now succeeded. So it now falls to you to find the fled members of the Vow, spread the holy lift-fruit, re-weave the broken diplomacy, and root out whomever it was that spread the plague deliberately.
It will not be an easy task, but you will not be alone. I have faith in the good nature of the remaining members of the Alliance. They will see sense, if you can but contact them and convince them of the truth of your cause.
Please, heroes. Rebuild this failing world, before it is too late for the remaining isles and their quarantines.