This idea feels weird IMO. Putting the creation myth of the sky archipelago solely on the backstory of a ducal house that is.
Because like, that would usually be the kind of thing reserved for the royal family's backstory and whatnot "We have the right to rule you as this archipelago only exists because of us", this kind of thing.
So... Cool idea, but IMO it doesn't fit the duke's status, I don't think anyone below royalty should have a house creation myth that is directly involved with the creation of the archipelago. Seems like it would be a bit too much of a good excuse for a coup, so royalty would have to do something about it.
*pat pat pat* You worked hard~