Devil in the Mist

In 2019, Devil in the Mist was released by Big Finish Productions.

Cover blurb
The TARDIS deposits the Doctor, Tegan, Turlough and their android ally Kamelion aboard a prison ship. A ship with just one prisoner: Nustanu, last warlord of the Zamglitti — monstrous, mind-bending mimics able to turn themselves into mist.

A ship that's in trouble, and about to make a crash-landing...

On a planet of mists.