Along with Tegel Manor (by Bob Bledsaw) and his earlier Caverns of Thracia, Paul Jaquays' Dark Tower is probably one of the most famous and well loved adventure modules ever produced by Judges Guild. So great is its reputation that it even made Dungeon's "30 Greatest D&D Adventures of All Time," the sole non-TSR/WotC product to appear on a list that, by my lights, was filled with lots of self-congratulatory nods to modules of little lasting import.
As I said in commenting on the Dungeon list, I think 1979's Dark Tower certainly deserves to be on Top 30 list, as, like most of Jaquays' work, it's masterfully done. I personally don't consider it his best -- I prefer Caverns of Thracia -- but there's no arguing that it's a brilliant piece of work. It's also noteworthy because it's an AD&D module rather than a OD&D one, which only makes sense given its late date. At this point in time, Judges Guild still held a license from TSR to produce official support products for their games and AD&D was the "rising star" in TSR's stable. Mechanically, though, this makes little difference, because, with a few small exceptions here and there, it's perfectly usable with OD&D and I suspect many people used it in such a fashion.
The module itself concerns the town of Mitra's Fist, formerly the hermitage of its namesake before he achieved apotheosis as one of the greatest gods of Law and Goodness. During his mortal existence, Mitra opposed the serpent-demon Set, who himself achieved divine status and sought revenge on his rival by creating a dark tower in Mitra's Fist, out of which poured his minions, who destroyed the town, its inhabitants, and, most importantly, the priesthood of Mitra who tended to the shrine of their deity's ascension here. Of course, over time, treasure seekers returned to Mitra's Fist, under the watchful eye of the clerics of Mitra, hoping to uncover some of the lost treasures buried in the rubble of the town. Unfortunately, in doing so, they have awakened the ancient evil of Set's dark tower and, unless someone acts to defeat it, history may repeat itself.
The dungeons consist of four levels that represent the buried ruins of Mitra's Fist, plus the eponymous Dark Tower and the Tower of Mitra, both of which were also buried when Set's minions destroyed the town. These areas contain a good mix of encounters, tricks, traps, and oddities. In addition, as one might expect from a Jaquays module, there are various antagonistic factions with which the PCs must interact, the results of which affect their progress in exploring the dungeons. Fascinatingly, the possibility of evil PCs aligned with Set is noted and there are even rules for the bonuses clerics of that god get while in areas dedicated to their deity (the same is true for clerics of Mitra).
Dark Tower has a lot to recommend it, chiefly its open-endedness. While not as large a complex as Caverns of Thracia, there's plenty to do here and, beyond the basic background that gives context to the whole place, there's no plot or purpose to get in the way of some good old fashioned dungeon crawling. The module is tough and unforgiving. It assumes a party of 6-10 characters of level 7-11; anything less than that I expect it could easily turn into a bloodbath in a few places. I understand this module was re-released under the 3e rules, but I've never seen a copy. If anyone has any experience with it, I'd love to know what it's like.