The chapter briefly introduces fantasy on stage and its position in the current state of research. It defines fantasy as a set of recognisable iconography related to the existence of sub-created secondary worlds. The chapter examines the concept of storyworlds as transmedial imaginary totalities pertaining to a specific fictional space. Fantasy on stage then refers to any actualisation of a fantasy storyworld on a theatrical stage. The chapter argues that fantasy theatre employs a series of tools and techniques to actualise, i.e. realise the said storyworld in such detail that it appears omnipresent and transcends the time-space limitations of a performance. Transgeneric theatre, i.e. theatre borrowing from other genres, increased narrativisation, affective promptings, and multisensory stimulation, all contribute to the actualisation of the chosen storyworld and demonstrate how theatre becomes a part of a wider transmedia network surrounding fantasy.