India, Oct. 13 -- That terrifying sound often comes in the middle of frozen nights, when the valley lies under snow, the rivers are trapped beneath ice, and the air feels ready to crack. It rings out like a thunderclap: "Whaaap." A pause, and then again: "Whaaap." It drifts through the mountains like something alive, heard but never seen. Those who recognize it call it the Yach.

The Yach is neither animal nor ghost, neither storm nor spirit. It belongs to a belief older than explanation, a spectral guardian of Kashmir mountains whose presence is felt rather than seen.

Advertisement ADVERTISEMENT "When we were children, our grandmothers would tell us to stay quiet when we heard it," recalls 72-year-old Ghulam Nabi from Gurez. "They said...