From the publishers blurb:
On the edge of a swamp beneath an old forest lay an even older fort, constructed for some ancient and unknowable purpose. The shadows are stronger here, and the scent of madness lingers in the air. The fort may seem mundane at first glance, but you will learn soon enough that something is not quite right...
This dungeon is ideal as a secondary starting adventure for Characters levels 1 thru 4. The difficulty is moderate, and even an experienced group may find themselves dying a fair bit. There is plenty of treasure and magic items within to reward those who are clever or determined enough to crack the Sunken Fort.
Includes 80 content-rich rooms with unique monsters you've never seen before. There are 3-ish areas, two of them themed, and one that is a maddening pile of rooms whose contents are entirely unpredictable. This Fort also guards the entrance to the Descent into Madness, a future mega-dungeon not yet ready for sale.