This book is an in-depth analysis of participatory worlds, practices beyond the mainstream models of content production and IP management that allow audience members to contribute canonically to the expansion of storyworlds, blurring the line between the traditional roles of consumers and producers. Shifting discussions of participatory culture and cross-media production and consumption practices to more independent media contexts, the book explores the limits, borders and boundaries of participating in today's digital media storyworlds. The text examines how audience participation works, identifying opportunities to make it a meaningful practice for audiences and an asset for IP owners, and discussing the challenges and barriers that the application of participatory culture brings along. The book defines what meaningful participation is by introducing the concept of 'intervention' and explains a range of factors impacting the way in which participatory worlds and relationships between producers, audiences and the world are shaped. This volume will be of great relevance to media practitioners, scholars and students interested in transmedia storytelling, fandom, literary studies and comparative literature, new media and digital culture, gaming and media studies.