Publication:The Keep on the Borderlands
Player characters begin by arriving at the eponymous keep, and can base themselves there before investigating the series of caverns in the nearby hills teeming with monsters. These Caves of Chaos house multiple species of vicious humanoids. Plot twists include a treacherous priest within the keep, hungry lizardmen in a nearby swamp, and a mad hermit in the wilderness. It typifies the dungeon crawls associated with beginning D&D players, while permitting some limited outdoor adventures.
When The Grand Duchy of Karameikos edition of the Gazetteer series was published, the Keep was given a specific location in the Known World of Mystara, in the Atlan Tepe Mountain region in northern Karameikos.
The Keep on the Borderlands was published in 1980. It consists of a thirty-two page booklet with an outer folder; the module was written by Gary Gygax, with cover art by Jim Roslof and interior illustrations by Erol Otus. It is designed for use with the Dungeons & Dragons Basic Set. It was included in printings 6–11 (1979–1982) of the Basic Set, although it was also available for sale separately. The cover of the first printing included the notation, "With minor modifications, it is also suitable for use with ADVANCED DUNGEONS & DRAGONS"; this was removed from later printings.
The module's cover notes that it is especially designed to help beginning players and Dungeon Masters (DMs). Tips for running encounters appear throughout the text to assist beginning DMs. The module also provides rudimentary rules for wilderness adventures, as these were not included in the D&D Basic Set. The structure of the adventure as a series of separate caves allows segmented playing sessions for beginners. The module has been described as a low-level introductory scenario, which leads the player characters from an outpost on the frontier of law into the forces of chaos.