A card game, "Illuminati", inspired by the trilogy, was created by Steve Jackson Games. Using the "Illuminatus!" books as "spiritual guides but not as actual source material", it incorporated competing conspiracies of the Bavarian Illuminati and Discordians and others, though no characters or groups specific to the novels. A trading card game () and role-playing game supplement ("GURPS Illuminati") followed. The instruction booklets' bibliographies praise the novel and Wilson particularly, calling "Illuminatus!" in part "required reading for any conspiracy buff". Robert Shea provided a four-paragraph introduction to the rulebook for the Illuminati Expansion Set 1 (1983), in which he wrote, "Maybe the Illuminati are behind "this game." They must be—they are, by definition, behind "everything."" Despite this initial involvement, Wilson later criticized some of these products for exploiting the "Illuminatus!" name without paying royalties (taking advantage of what he viewed as a legal loophole).From article "In the RAW: Necessary Heresies" originally published in REVelation magazine (#13, Autumn, 1995) pp. 36–40. Available at Disinformation website . Retrieved 28 February 2006.</ref>