From PathfinderWiki

The Drillstones is one of the many Thassilonian ruins in the wilds of the Linnorm Kingdom of Southmoor. More than three dozen spire-like, 60-foot-tall stone monoliths rise from the northern Kodar Mountains foothills 50 miles southeast of Kopparberget. Each of these monoliths is decorated with strange spiralling gouges, almost as if they were immense drills sent up from underground. Each stone vibrates slightly to the touch, but some nights of the year these vibrations increase into a disturbing buzz. The stones' purpose is unknown, but a mysterious doorway was recently discovered at the base of one of the monoliths that leads to a strange labyrinth, and deactivated clockworks were found inside. Some scholars believe that the Drillstones were the upper edge of a war machine buried underground.1


  1. Matthew Goodall, et al. “The Linnorm Kingdoms” in Lands of the Linnorm Kings, 27. Paizo Inc., 2011