Tomb of Horrors is an adventure module written by Gary Gygax for the Dungeons & Dragons (D&D) role-playing game. 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. The module, coded S1, was the first in the S-series, or special series of modules. Several versions of the adventure have been published, the first in 1978, and the most recent, for the fifth edition of D&D, in 2017 as one of the included adventures in Tales from the Yawning Portal. The module also served as the basis for a novel published in 2002.