Beneath the black rocks of eastern Kenya, the land splits open into a secret underworld — a labyrinth of ancient caves formed over millions of years. For generations, custodians like Lugadi Runya Shipa have guided worshipers through the caverns, just as his father and grandfather once did. In one chamber, he offers thanks to the spirits, sometimes by sacrificing a goat. “I know they can hear me,” he said in the darkness. But for the past five years, Mr. Shipa and his community have fought a battle few believed they could win, when an Emirati-backed company aimed to bulldoze over 600 acres of land — including most of the caves — to make way for cement production.