Instructions
Venture into Westfall, which borders Elwynn Forest and Duskwood on the Eastern Kingdoms continent. If you enter from Elwynn Forest, run south until you reach Moonbrook. If you enter from Duskwood, run east until you run into Moonbrook.
Enter the southernmost building in Moonbrook. The building is the second largest in the town and looks like a large barn. Continue through the building until you reach a tunnel. Run through the tunnel and keep on the straight path until you see a bridge. Turn right and follow that path. You'll eventually enter a large room with a path that splits left and right. Follow the right path.
Jump off the ledge to the right once you reach the next room. Run ahead and jump into the purple aura to enter The Deadmines.