Ramping up my reviewing.
Happily playing games for many, many years.
D1: Descent into the Depths of the Earth is the first of 3 modules in the "Descent" or "Drow" series, and the fourth of 7 modules in the special progressive campaign series generally known as the GDQ series.
First published in 1978, the adventure picks up after the end of the Giant series, with the adventurers pursuing the fleeing drow elves into a long tunnel deep under the earth. Apart from the author (Gary Gygax) and a few legible signatures on the artwork, no credits are given for this adventure.
It's worth noting that the artwork, mostly(?) by Dave Sutherland, is quite poor. Some pieces buck the trend and look rather special - and are likely done by Dave Trampier - but mostly it is disappointing. I assume that DCS also did the maps, which are good.
One of the fascinating things about this adventure is that a large part of it is the travel through the tunnels of the underground on the way to three set-piece encounter areas. The player's map and DM's map show the tunnels of the underground in one of three forms: primary, secondary or tertiary, and example maps of how those tunnels appear are given, along with extensive random encounter tables. As a check for encounters is given each mile (hex) of the maps with a 1 in 10 or 1 in 12 chance, it's likely that only one or two random encounters will occur before the end of the adventure; that said, the tables are then used in the next two adventures.
The development of the D&D stat block continues here after G1-3, and why the later form was developed becomes painfully clear. Here's an example of a "stat block" in this adventure:
11-16 bugbears (H.P: 15 each) with ring mail jacks and large shields (AC 3) and each armed with heavy morning stars (+2 on damage) and 2 heavy spears.
It gets worse when we reach the drow:
Each Drow merchant is male and a cleric/fighter of 4th/4th level (H.P: 18; +3 chain mail, +3 buckler, +1 for dexterity of 15 for an overall AC of -3). Each is armed with a +2 mace. They have the following spells... and so on and forth for another 5 lines.
Detailing where each of the parts of AC comes from might be necessary, but the verbose style does make it difficult to identify exactly what their final stats are.
The first two keyed encounter areas detail a drow checkpoint (which must be encountered) and a mind flayer spy post (which can be avoided). Both are described as combat encounters, with little thought to negotiation. The drow checkpoint is particularly interesting for the insight it gives into the culture of the drow: there are two separate patrol groups (male and female), which are rivals with each other. One also gains more insight into the opposition to Eclavdra's plans with the giants from the Fane of Lolth.
The final encounter area is actually a big setting in itself: the caverns and warrens of the troglodytes, which takes up a map of two panels on the gatefold cover. 40 encounter areas in the caverns are described, and there's a lot of combat or negotiation to be had: from the drow overseers, to the hidden lich, to the bugbear servants of the drow, to the pack of ghouls and ghasts, and of course to the troglodytes.
All in all, the caverns show how the inhabitants of this underground realm are controlled by the drow elves. As an adventuring locale, it's perhaps more interesting for the variety of foes to best and the treasures to be won, although there are a few nice Gygaxian touches throughout.
This part of the adventure has covered the first 11 pages. The 12th page is given to a description of the Jermlaine (Jinxkins) who appear in the random encounter tables for the tertiary tunnels and not further in the adventure: they're rather boring, actually. 1' tall humanoids? They don't add that much to the adventure.
The final four pages are one-sided (so two pages of information), both perforated, one with the player's map of the tunnels (as dropped by the drow in G3), and one with DM maps for tunnel encounters.
This isn't the most challenging of adventures. It's theme is evocative, but the intensity of the challenges have dropped since G3. This is intentional, for the final two adventures would be significantly more difficult to play and to run, and a gentle introduction into the depths of the earth was required.
One note: if the players would be so perverse as to move off their copy of the map into the unexplored reaches of the Depths, the DM did have a full map of the area and where the tunnels lead and where the major encounters areas were... but detailing of those encounter areas was up to the DM. Perhaps the most evocative of everything in this adventure is a small area on the DM's map entitled "The Sunless Sea", which would be referenced again in D3 Vault of the Drow.
I'm quite fond of D1: it might not have the impact of the later adventures, but the concept of these extensive tunnels under the earth was exciting, and it provided the germs of later scenarios. Not a great adventure, certainly, but an interesting one.