The Siege of Durgam's Folly

From the website:

"An embattled outpost at the edge of the wilderness has finally been overthrown. Strange creatures patrol the land. A local hamlet is in ruins. But just who-or what-has taken over this once mighty fortress? An adventure for 4 to 6 characters level 5 to 8. Contains a strange new set of monsters that will plague your campaign world for years!"