Visit the Abyss. Meet Demon Lords. Kill Everything.
In the heart of the Demonweb, Lolth surveyed the Grand Council Chamber and the demon lords assembled by her invitation. Throaty growls indicated a dispute among Yeenoghu's pack. Obox-ob's insect swarms chittered while Demogorgon ranted from the central podium. The other emissaries seemed restless. Across the hall, Graz'zt met Lolth's gaze and smiled. The demon queen shivered with a tingle of foreboding.
This Dungeons & Dragons adventure takes heroes from the planar city of Sigil to the darkest corners of the Outer Planes, gathering resources to battle the forces of Lolth, Demon Queen of Spiders. The heroes must navigate a carefully spun web of treachery and deceit to reach the violent heart of Lolth's domain and put an end to her sinister dreams of conquest.
According to Wolfgang Baur in this thread:
Yeah, I wrote this one, but unlike Ravenloft, the goal was not to remake Q1. It's a plane-hopping adventure in the Abyss, though, and that's not a bad thing.
I was fortunate that I had an advance copy of the Fiendish Codex to work with as well; some of that material shows up in the adventure.
Uh, I wrote roughly 140,000 words, and Gwendolyn did 30,000 or so. So, I think that makes it a 224-page hardcover, just like Ravenloft. It covers levels 9 to 12, and has a metric ton of tactical maps, combat breakouts, more than a dozen new monsters. It is filled with creepy evil goodness.
Unfortunately, it was written in an incredible hurry, to meet a tough deadline, so those are all the details I can remember.... ;)
I forget whether it's completely generic (it's been 7 months since I touched it), but it is a planar adventure, so really, it doesn't require you to go through G1-3 and D1-3 first.
There's a nod to Erelhei-Cinlu (since that's the drow city I always default to), but really, it's not about the material plane. It's about the Abyss, and a few other places.
