Chokestone

This place, and the lands around it, are deserted, not farmed by anyone. The site is that of a great battle between Aerdi men and a small Flan tribe in -171 CY. The Oeridians were easily triumphant, and an excessively brutal general ordered the torture and sacrifice of all surrendering Flan folk in thanks to Erythnul. The following day, the Aerdi army woke from its camp to find that the land for several square miles around had been stripped of vegetation. Only slate-like stone remained. As they trod upon the stone, it cracked as if it were brittle paper, releasing clouds of oily, choking smoke. Less than a third of the army managed to march away from the accursed area, and those who survived suffered lung infections and disease which brought their lives to very premature ends.
From time to time since this slaughter, a huge black smoky serpentine shape has been spotted prowling the lands around Chokestone, slaying any who dare approach the land where the Flan were slaughtered. Astrologer-sages can predict this wandering; it occurs around once every 17 years, with the “snake” manifesting for 2-12 days. At other times, mages will sometimes try to obtain some of the stone for use in making dust of sneezing and choking, but they invariably send servants to obtain it rather than risking entry themselves.