Arduin is a fictional universe and fantasy role-playing system created in the mid-1970s by David A. Hargrave. It was the first published "cross-genre" fantasy RPG, with everything from interstellar wars to horror and historical drama, although it was based primarily in the medieval fantasy genre. Development history Arduin was one of the earliest challengers to TSR's Dungeons & Dragons. It began in the mid-1970s as a personal project Hargrave created to share with friends, but became so popular that he was inspired to publish the material. Hargrave was one of several early RPG players from the San Francisco Bay area to also become a game designer, having started by creating variant rules for his weekly Dungeons & Dragons campaign which was heavily house-ruled and included hundreds of players, with its setting of Arduin, a neutral ground situated between nations formerly at war with each other. Around 1976 Greg Stafford of Chaosium played in Hargrave's Arduin game for a while, and he approached Hargrave asking to publish his game system as "The Arduin Grimoire"; the book was placed on Chaosium's publication schedule for February 1977 to be the company's first role-playing game release, but when the company received an incomplete manuscript Stafford instead rejected it. Hargrave self-published The Arduin Grimoire in 1977 and two follow-up Grimoire books in 1978, and the three books became known as The Arduin Trilogy. They are, in order, The Arduin Grimoire (1977), Welcome to Skull Tower (1978), and The Runes Of Doom (1978). The Arduin books attempted to add many interesting and notable features to the fantasy role playing milieu. In addition to new rules, the Arduin Trilogy contained unique new spells and character classes, new monsters, new treasures, maps, storylines, extensive demonography, and all sorts of charts and lists which detailed the Arduin "multiverse", many of which were new to role-playing gamers of the time. While the original series of Grimoire supplements were intended as supplements for original Dungeons & Dragons, mention of D&D was prohibited legally. Although the Arduin books did not explicitly claim to be a Dungeons & Dragons supplement, they were treated as such by most users. As follows, there was contention in the RPG world that the Arduin system lacked cohesion. It was only with the publication of the later book The Arduin Adventure (1981) that a true standalone system began to evolve, where other systems were not needed to adequately