Travel to Plaguewood, northwest of Light's Hope. Destroy 8 Scourge Structures by using Smokey's Special Compound at the Mark of Detonation planted inside each building. Smokey has had the Ziggurats and Slaughterhouses marked.
Once you plant the bomb, leave the building and marvel at your handiwork.
By the way, Smokey's Special Compound is rather... unstable.