- You may be looking for the Ethereal or the short story of the same name.
The Ethereals were a humanoid race native to an Earth-like planet. Their capital city was Droog. The Ethereals built the Baggolts to serve them, but the Baggolts rebelled and turned their former masters into living clouds in a failed attempt to vaporise them.
Five eketrons later, the First Doctor visited their world, where the Ethereals captured him and tried to turn him into a cloud for new humanoid bodies, a process which would have killed him. Instead, the Doctor restored their original bodies, then helped their leader Mitzog put an end to the Baggolt rebellion. (PROSE: The Cloud Exiles)
Several Ethereals were among those trapped on Denossus when it was transported to the Time Vortex by the Vortexians. They would remain trapped for over twenty years until the Vortexians were expelled by the Second Doctor. (COMIC: Land of the Blind)
An Ethereal visited the Dalek Dome on Earth in 2023. (COMIC: Liberation of the Daleks)