[Sorey's exclamations are actually pretty freaking adorable, and he can't hide a smile even as he's faced with a barrage of questions. They have a little time on the lift so he can oblige.]

It's a mixture of seraphic artes and Rolance ingenuity, [he explains patiently.] Humans made something as light and buoyant as possible with the ability to steer. And some wind seraphim were able to use artes to make a gas that was lighter than normal air.

They use a machine to control the pressure inside the big pockets on top and a bunch of rudders. Fish have little bladders in them, that's how they float or sink. It's the same principle.