The God that lived in the mountain is gone, dead or fled to some other realm. His cavern is empty, a throne room of delicate crystal spikes that sparkle in torchlight; I am one of a very few lucky and brave enough to have seen it.
What spelled his doom? Did the Water-God murder him? There are pools in the cavern, pristine-looking but poisonous, at least to men. If the Mountain-God was foolish enough to drink from it, would it have killed him? What is toxic to a God?
The Priests have no answers… hardly surprising. We may never know.