Cloud

A cloud was a collection of moisture in the atmosphere. They were the source of rain.

One day whilst in his village's market, Moop noticed that the clouds were making strange shapes until a face appeared in them. It claimed to be the creator of Moop's people and asked for a tribute. Moop gave the "god" some of his Grunt. (PROSE: The Tomorrow Windows)

After losing his companions and parents-in-law, Rory Williams and Amy Pond, the Eleventh Doctor 'parked' his TARDIS in or before 1892, atop a cloud, high above London. A staircase provided the Doctor a means of inconspicuous entry access to and egress from the surface, while assuring him solitude. (TV: The Snowmen)

In the early 21st century, flying Cybermen led by a female incarnation of the Master, 'Missy', took to the skies and created clouds of cyber-pollen above Earth's graveyards. These clouds then rained upon the graves, recruiting the dead into a new Cyberman army. When control of the Cyberman army went to the hands of the recently-converted Danny Pink, he ordered all Cybermen to return to the clouds and self-destruct, destroying themselves and the clouds. (TV: Death in Heaven)