So this is coming out later this month, my alternative follow up to the giants series instead of descent. You can of course use it for any floating cloud castle needs you have...
The hot and smoky badlands of the King of the Fire Giants lies behind the party: his great hall, once a symbol of his power and authority, now only a memorial to his terrible defeat. Within this hold, the party found information leading them onward in their quest to find the fearsome mind behind the recent giant uprising.
Their journey has been long and tiring, but the end of the task lies ahead. A gigantic spire of a mountain rises into the sky. Around the misty peak, an unusual cloud hangs, as if tethered to the stony expanse itself, and upon this strange cloud a mighty brass-roofed castle stands. Perhaps it is here, among the peaks and the mist, that the source of the giants' evil may be found?