Cloud Dragon
D&D
Cloud Dragons are reclusive and aloof creatures from the Greyhawk setting. Their breath weapon is a blast of freezing air and ice crystals. They can assume a gaseous cloudlike form at any time. Their scales change color as they age, starting silver white with a tinge of red, then red, then orange, then red-gold. Though they can eat almost anything, their diet is mainly water and silver. They live in magical cloud islands. They have no respect for any creature who can't fly without the aid of magic.
Pathfinder
In Pathfinder 2e, cloud dragons are planar dragons from the Elemental Plane of Air. They can also turn into clouds of gas, and their bite deals sonic damage. Their breath weapon is a line of electricity.