Secrets of Tsojcanth: Caverns of the Vampiress (2005)

A One-Round Living Greyhawk Core Adventure

High-Level: Caverns of the Vampiress

From the introduction:

Stirrings of a dark malevolence in the Yatil Mountains draws the followers of terrible forces to a once-used demesne of Iggwilv, the Witch Queen. At the behest of others, you journey to the Lost Caverns of Tsojcanth to confront the evil that lurks there and unveil its deadly secrets.

This adventure is divided up into three levels of play (low level, middle level, high level); each player may only participate in one of them.

A challenging special adventure for characters levels 11 - 17.