Tomb of Horrors is a 1978 adventure module for the Dungeons & Dragons role-playing game, written by Gary Gygax. It was originally written for and used at the 1975 Origins 1 convention. Gygax designed the adventure both to challenge the skill of expert players in his own campaign, and to test players who boasted of having mighty player characters able to best any challenge. Numbered "S1," the module was the first in the "S" (for "special series") series of modules. Several versions of the adventure have been published, the first in 1978 and the most recent, published for the fourth edition, in 2010. It also served as the basis for a novel published in 2002.