From PathfinderWiki

The spheres are a strange, mysterious feature that dot much of the Elemental Plane of Air. The spheres, as their name implies, are massive spheres of steel and bronze covered in an ancient, immense script carved into their surface. Records from the most ancient archives of the Djinni Empire indicate that these carvings were once much deeper, but uncountable ages of relentless wind have slowly started to wear them away. These symbols defy all translation, even magical, and no one has ever been able to penetrate the spheres via any means. Attempts to use divination magic to look inside the spheres reveal images of a churning mass of bloody teeth that have been known to drive the viewer mad. Those who have consulted the very gods themselves about this mystery note that the most ancient deities seem to show a flicker of ancient regret or remorse before refusing to say anything more about them.1

The djinni, natives of the Plane of Air, treat the spheres as deeply taboo, and perhaps with good reason. Many of the settlements and buildings that have been built atop the spheres over the eons (as they are one of the few points of solidity on the plane) disappeared completely, leaving not even the slightest trace of their existence. Some have speculated that whatever lies within the spheres is some sort of ancient rival to the djinni from the depths of pre-history. The spheres have fascinated many across the ages. Currently, a human Pathfinder monk named Zennia Lyn plots the paths of numerous spheres, believing that their movements are not in fact random but actually predict massive cosmic events. Zennia has already seen positive results from her studies, glimpsing profound unguessed at truths but her studies have upset the djinni, even now they move against her, hoping to thwart her plans or maybe even worse.1