A One-Round Living Greyhawk The Splintered Sun [Meta-]Regional Adventure
From the introduction:
The revenue brought in by gemstones panned from the River Thelly is vital in the maintenance of the war-damaged city walls and defences of Nulbish. The Royal Guild of Merchants need guards to protect a keelboat full of grain and gemstones destined to be sold at Kalstrand for the Windmarch fair. The Ahlissan army after all routed many bands of outlaws and humanoid tribes during the recent campaign around Wyverntor, and these are desperate for coin and food.