From PathfinderWiki

The Drillstones is one of the many Thassilonian ruins in the wilds of the Linnorm Kingdom of Southmoor. Just over 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 purpose of the stones is unknown but a mysterious doorway was recently discovered at the base of one of the monoliths, leading down to a strange labyrinth. Deactivated clockworks have been found inside the structure. Some scholars believe that the Drillstones was the upper edge of a war machine buried underground.1