Strahd's Choking Fog

Strahd's Choking Fog is a ring of toxic fog that encircles Castle Ravenloft and the Village of Barovia.

A living creature passing beyond the outer limit of the ring of fog is overcome by a fit of coughing that does 1d4 points of temporary Constitution damage per hour (no saving throw) until the victim dies. Lost constitution can only be restored by returning wihtin the ring. The Vistani sell, at the discretion of Count Strahd von Zarovich, an elixir that allows safe passage out of the ring of fog.

Data from the Ravenloft Catalogue

		Secrets of the Dread Realms Domains of Dread House of Strahd Ravenloft I6
		Secrets of the Dread Realms - p12 Domains of Dread - p59 Realm of Terror - p64
		Secrets of the Dread Realms - p12 Domains of Dread - p59 House of Strahd - pp6-7 The Ravenloft Campaign Setting:Domains and Denizens - p8 Vampire of the Mists - 26,28,44-45,302 Realm of Terror - p64 Ravenloft I6 - pp14,18