Although this came out in 1984, it harkens back to much earlier stage in the development of AD&D. In fact, it’s a part of the earliest possible iteration of D&D, having been developed by Gary Gygax in the early 1970s as part of his Greyhawk campaign. It’s from his campaign that the whole of the game was then developed.

As can be seen from the title, this adventure focuses on Mordenkainen, but it also brings in his companion Bigby and a couple of other characters that were part of the Kuntz/Gygax home game. 

As was also typical of that period the adventure is very much a kind of funhouse, hack and slash affair. Here Mordenkainen and friends hear of a couple of impenetrable doors underground in the abandoned Maure Castle. Managing to go through the doors they get into the several levels of a dungeon which eventually culminate with a demonic “boss fight”. Fun stuff.