In Japanese folklore, when too many people die and no one buries them, the bones accumulate. Individual identities dissolve. What remains is a collective fury that merges into something fifteen meters tall, with eyes that glow like foxfire and teeth that grind in the dark.

The Gashadokuro, the rattling skull, is a skeleton taller than the trees, assembled from the bones of hundreds of forgotten dead. It hunts at night during the hour of the ox, between one and three in the morning, when the boundary between the living and the dead is thinnest. It cannot be killed with swords. It persists until the accumulated rage of the dead burns itself out. That can take decades.

In this episode, we trace the creature from the ninth-century Nihon Ryoiki, a Buddhist text where a skull in a field speaks the story of its own murder, through the rebell ...