From publisher blurb: Pan, His Majesty in Yellow is a fairy tale cosmic horror sandbox campaign setting that combines the lore of Peter Pan, Hastur, Neverland, and Carcosa into a strange and unique experience. This version is designed for use with Old-School Essentials Advanced Fantasy, and is therefore compatible with the BX edition of the world's most popular roleplaying game—as well as most OSR games and retroclones.