Immediately after writing Under His Skin, I was looking for inspiration. And I found it in a particle effect in Skyrim. I thought, wouldn’t it be crazy fun to have the party having to escape a collapsing tunnel? They’d be trapped underground, and have to find their way out, and it would be a grand old time!
So, then I wrote It All Falls Down. The Saatman Emerald (which at the time was just a name I picked out of the air, but I later reference in the Saatman’s Throne Adventure Path) is stolen by a bunch of crazy duergar, and as the PCs chase after them, they start the tunnel they were making collapsing to cover their retreat.
Cue being trapped underground.
There’s a lot of fun stuff in this adventure, including some new bug-mounts, a haunted well, and a half-dozen ways out of the cavern system. And, my playtesters, and the reviewers (it got 5/5 stars) all agree with me there.
You can find It All Falls Down here, on Paizo.