Participatory culture transformed audiences into active contributors, but conversational AI and generative systems are beginning to reshape participation into something more enduring: inhabitation. This essay argues that we are witnessing the emergence of a new narrative medium in which people develop persistent relationships with responsive storyworlds that remember, adapt, and evolve alongside them. Drawing on decades of work in transmedia storytelling, tabletop roleplaying, and franchise architecture, Jeff Gomez introduces the concepts of the Mythic Field and upstream authorship to explore how coherent systems of meaning can persist within inhabitable worlds. As storyworlds become places where people rehearse identity, relationships, and values, the challenge shifts from simply expanding stories to intentionally designing worlds worthy of being inhabited.