Coined by Richard Saint-Gelais, the concept of transfictionality describes a process whereby characters, locations and events inhabit and share the same narrative space. The introduction of the multiverse concept, of a nexus of parallel worlds with the Dark Tower as lynchpin, afforded Stephen King the opportunity to begin constructing transfictional bridges between two incommensurable worlds in order to fuse them together. In 1999, King was involved in a life-threatening accident, and Roland's quest was in peril, The Dark Tower verging on collapse. In 2004, the final volume of The Dark Tower spelled the end of a four-decade journey for King. This would allow for the emergence of an expanded universe spearheaded by King's author-function as creative consultant, but which would become trans-authorial and transmedial. As a case study in worldbuilding, the Stephen King Multiverse shows that transmedia storytelling is but one element in a complex chain of trans-associations.