A One-Round Living Greyhawk Highfolk Regional Adventure
From the introduction:
True darkness has fallen over Quaalsten in the heart of the Vesve Forest. Two armies of evil lay siege to it, and those in Highfolk and Flameflower struggle to provide aid to the beleaguered town, all the while preparing themselves for the inevitable conflict if it is lost. The minions of the Old One have waited long for this day, and it's up to a few brave souls to deny victory to the terror that stalks the ancient forest.
An adventure for selfless, heroic PCs of levels 1-12.
Blood on the Trees, Part 1.