From the Back of the Book:
The Mists of Ravenloft lead to G'Henna, land of famine and zealous devotion to Yagno Petrovna, high priest of the Beast-God Zhakata. In the cities of G'Henna, worshipers starve themselves to prove their faith; in the Outlands, twisted mongrelman struggle to survive in a land of unforgiving windstorms and bleak plains.
No domain in the Demiplane of Dread has been in greater need of change--and the subtle agents of the Circle of Darkness wish for nothing less than the overthrow of their oppressive leader and create a new order lead by Zhakata himself.
They should be careful what they wish for.
Circle of Darkness is a dangerous adventure for heroes willing to face not only the Dark Lord of G'Henna, but also the greater evil which threatens to overcome him. The fate of an entire domain is in the heroes' hands.