The first of the TSR produced adventure modules not written by Gygax, this was bundled with the basic D&D box from the fourth printing until 1980 when it was replaced by Keep on the Borderlands (B2). So for a short while, mainly in 1979, this was what you would get in the basic set. I think you could also buy it separately, but I’m not sure about that. Anyway, it was a common module around that time, and although it’s made for Basic D&D, it has instructions to adapt it to AD&D, which is really not that different at the early levels that this adventure is made for.

It’s clearly a beginner’s module and as such it has a lot of instructions for new players and particularly for a new DM, on how to play the game, how to populate the dungeon and so on. In fact this is a bit of a hybrid sandbox module, seeing as it has a dungeon and keep to explore, but it asks the DM to populate the dungeon with monsters and treasure, leaving a little space in each room description for the DM to fill in the encounters and treasure to be found. Of course there are tables to help the DM do this.

As the story goes it’s very barebones, a couple of adventurers, a warrior and a magic user, built a keep which has now been abandoned as they are presumed dead. The players hear about this and decide to explore. That’s it. Curiously though, the disappeared adventurers are repeatedly described as evil, but they seem like a couple of ok guys, you find loads of like “Employee of the Week” artefacts in the dungeon and even a funny “suggestions on how to improve the keep” report by their right hand man… they just seem like they run a nice workplace… I dunno.