This master thesis seeks to clarify the concept of Role-Playing Game as a fundamental inspiration for the creation of the author’s fictional prose text entitled "Mysterious Islefort", which is staged in a video format and for which the costume design was realized. Thesis describes the origin and historical development of Role-Playing Games (RPGs) from war games and simulations to the emergence of fantasy literature as a key occasion for the emergence of what would become known as the Role-Playing Game. Furthermore, the types of RPG under four basic forms are explained, namely Tabletop Role-Playing Game (TRPG), Live Action Role Play (LARP), Computer Role-Playing Game (CRPG) and Multi-User Dungeon (MUD). Thesis includes character classes within a fantasy RPG, with a basic division into human classes and demihuman classes, or races. Special attention is paid to the creatures and monsters that appear in the fantasy RPG, and the emphasis is on those that appear in the prose text "Mysterious Islefort". Thesis also mentions two significant movies that are based on the RPG, but according to the genre, they process it in a completely different way. The constituent part of this master thesis is the author's fictional prose text “Mysterious Islefort” and a costume design for characters for the performance of prose text in video format. The costume design was preceded by an analysis of the characters, the creation of a conceptual map of the costumes and costume sketches. After that, three costumes were made for the two main characters and one supporting character, and finally "Mysterious Islefort" was performed in video format.