Sky kraken

A large cephalopod creature that grows a strange magical shell that is able to float into the air. It's shell is spiral cone shaped but double sides, one pointing up and one pointing down. It's face is like that of a nautilus with several squid like tentacles. Four of it's ten tentacles are different, adapted into wide flat fans that allow it to push itself through the air as it's shell keeps it afloat.
They are able to breath both in water and in air but often need to return to the water to rehydrate and hunt for food. They can control the buoyancy of their shells to a very high degree thanks to it's magical properties, creating large pockets of near vacuum levels of pressure, concentrated mostly towards the upper part of the shell to keep them upright.
Sky kraken rarely travel over land unless migrating to another body of salt water not far away. They are largely passive but have been known to attack ships both on the water and in the air when territorial or hungry.
Their shells are sometimes harvested and used in airships, although fighting a sky kraken is no easy feat and they aren't too common to begin with. So their shells a rare and valuable commodity.