Ardanyan's Revenge (2006)

From the back cover:

When the Scourge was imminent, the people of the town of Ardanyan sought shelter underground, expecting only the Horrors to be a threat. Over the centuries spent confined in the kaer, small quarrels grew into conflicts, which in turn developed into blood feuds and racial hatred. The Horrors would gladly have fed on Kaer Ardanyan - if they had only found it...

For generations, a secret society betrayed the unsuspecting citizens of Kaer Ardanyan - now they struggle to keep their terrible secret. The player characters are the spark igniting a bonfire of intrigue, deceit and illusion. The heroes have to be careful, however, not to fall victim to the flames while on their dangerous quest to save the residents of a lost kaer!