A navigational hazard and curiosity: a field of massive floating stones that drift through the central Alrock on unpredictable paths. The stones are porous volcanic rock, somehow light enough to float. Some are large enough to support vegetation. One supports a hermit's shack.
Ships navigate around Stonedrift carefully. The stones move slowly but unpredictably, and collisions are common. Some captains swear the stones deliberately block certain routes—as if they're herding ships toward something.