To be specific...the Goblin army appears in the hills to the south-southwest of that little village south of Harmondale. Light the three signal fires, enter Castle Harmondale, exit, then head due south from the front door. Having the FLY spell helps considerably. To get there on foot, go along the pathway into the hills immediately south of the village, but instead of crossing the bridge over the road to Barrow Downs, head south along that plateau.
