XR technologies are increasingly considered as expressive media with special qualities for narrative representation. In this chapter, we chart some of the major challenges inherent in the implementation of digital narratives in XR. For this purpose, we consider the intersections between different research domains like classical and post-structural narratology, cognitive narratology, literary studies, computer science, game research, cognitive science, and particularly interactive digital narratives (IDN) and storytelling. As with IDN, many of the challenges of implementing narratives in XR have to do with the trade-offs between interactivity and immersion. In this direction, we aim to contribute to the bridging between the IDN and XR research domains. We elaborate on specific issues in IDN that may require particular care in XR, such as agency, embodiment, narration, "point of view technologies, " artificial agents, and AI. Additionally, we provide examples of different application domains in games, serious games, cultural experiences, healthcare, and immersive journalism. To conclude, we highlight the eminent role of narrative cognition in XR and suggest a roadmap for combining XR technologies, cognitive sciences, advanced biometric signals processing, and storytelling techniques for investigating ways we interact cognitively with stories and the effects of XR narratives on the human emotional-cognitive system.