Another one of those classic modules by Gary Gygax that shows the genius and flexibility of the father of Dungeons & Dragons.. ""Shrine of the Kuo-Toa," the second adventure in this collection, was used as part of the D&D tournament at GenCon XI (1978)." What we're really dealing with is a solid exploration and tournament style adventure. Violence is not always the answer with Descent Into The Depths of Earth & mixing & matching campaign elements doesn't take away from this classic module in the least.
Let's begin by changing the Kuo-Toa to Deep Ones which gets in more in tune with the Clark Ashton Smith vibe & HP Lovecraft. There's a certain amount of the Hyperborean cycle within D1-2 with its foul verminous humanoids and Deep One style monsters. The inclusion of D2: "Shrine of the Kuo-Toa" (1978) gives the whole affair a foulness that sometimes seems to overwhelm the whole affair of the adventure which reminds me of HP Lovecraft's Shadows over Innsmouth. Originally the Drow were mysterious and merely a legend mentioned in the Monster Manual for Advanced Dungeons & Dragons first edition. Here in Descent into The Depths of the Earth their fully realized. I want them back to being weird, twisted, and completely dangerous beings of myth & legend. How can I accomplish this with my limited schedule? Well fortunately Gavin Norman has done the Complete Vivimancer.
Suddenly the Drow are far closer to the bio engineering terrorist nation of Cobra la and less of the fetish & leather crowd that players of later editions seem to love. Yeah that's much better and keeps things rolling along onto my 'Old Earth ' setting. So what exactly are the Drow now? These are Myrkálfar straight out of Norse mythology & legend twisted by super science of space gods eons ago. We see this in the Myrkálfar's god Atlach-Nacha lair later on.
Artwork used without permission from here
Ropers, Umber Hulks, & many of the iconic monsters of Advanced Dungeons & Dragons fit into alien and artificial breeding aspect laid out in this module. All of this ties back into the ideas of A.Merritt & Arthur Machen where the underworld is truly alien which is closer in keeping with the Underborea of Astonishing Swordsmen & Sorcerers of Hyperborea then the Underdark of AD&D's later books. All of these are factions in the inner Earth's various underworld adventure locations. This ties back into A.Merritt's 'Moon Pool' & the caches of alien technologies from 'The Metal Monster'.
All of this ties back in with the planet Cykranosh (or Saturn as we know it today) & with Tsathoggua. Whose machinations have been spinning for centuries leading the fire giants & Myrkálfar alliance. This leads into events happening on Hyperborea where the Deep Ones are beginning their push again for dominance of the land. This connects in with events from The Mystery At Port Greely!
Various caves, caverns, etc of the underworld have ruins & dimensional gate ways that lead off world across the planets & only the gods know where. The events depicted in D1-2 Descent Into The Depths of the Earth could be signaling that the stars are coming right as inhuman powers move the hands of the clock closer and closer.