From the introduction: Out in the deep valleys of the Cosanq Hills in Fnoi province a traveller might come across a massive boulder standing in the middle of a u-shaped vale. Some say it was left behind as the Great Glacier retreated, when the cosmic cycle shifted back towards Chaos from Concordance. Some say it was a missile cast by the mighty demon Falls-Mountain, a minion of the Divine Minister of the Shaking Earth. Some say it is the heart of the Cosanq, a fallen heavenly guardian made of iron. Some say it fell from one of the Wanderers. Truth is, nobody knows, perhaps not even the lone mystic who tends the temple within the Boulder Stone.