A One-Round Living Greyhawk Nyrond Regional Adventure
From the introduction:
King Lynwerd wants Blackmar Huldane brought to Royal Justice dead or alive. The former war hero Blackmar has been declared a traitor to the Kingdom of Nyrond and now has a substantial price on his head. Everyone in Mowbrenn knows that Blackmar has supposedly holed up in the old Barren Keep with forces loyal to him. So that is where you are headed.