The Bestiary Malitiae: Miasmic Fog
Another one for the Bestiary, this one with a Mothership stat block. Thanks to onslaught six for helping me edit this one!
Miasmic fog
On the coldest autumn nights, a strange fog may roll through the valleys. Swirling grey and white, the impenetrably dense mist is indistinguishable from normal fog, except the faint smell of rot that precedes it. Coming in contact with flesh jolts the fog to life, whipping it to a tempest that tears through any exposed flesh in its path.
There has been much debate as to whether the fog itself is alive or it carries something else that eats flesh; no samples have ever been recovered for testing.
[C:100 Necrotizing Fog 5d10 DMG]