Cloudkill

[kingpin]

Cloudkill says that you figure out the cloud's new spread each round based on its new point of origin, which is 10 feet farther away from the point of origin where you cast the spell.

So if you are flying, and cast it directly below you onto a flat surface, would it just stay in place?

[Adamantine Dragon]

GM call, it might be that the GM rolls a d8 and picks a random direction it moves once it hits an obstacle.