From publisher blurb:
When the dwarves of The Demon's Veins mine hacked their way into the side of a mountain searching for mithral, they found instead a large hollow and a demon lurking in the bottom of a crevasse. When the demon kept lurking instead of attacking them on the spot, they decided to make a little money on the side by roping off the crevasse and turning it into a tourist attraction. But the spawn of the Abyss next door is merely biding its time, waiting to for the right moment to strike. The dwarves have created a mess for themselves that only a party of brave heroes can sort out.
Path to The Demon's Veins is published under the terms of the open license for Pathfinder RPG. It is compatible with the First Edition Rules, but it also includes notes for running it with the Second Edition Playtest rules. It does not specify a particular campaign setting, and it is written to allow you to integrate it into your own campaign world by filling in various details. You can run it as a stand-alone, or as a sequel to Found by the Way #5: Path to Jarnborg.