From publisher blurb:
Flik Silverpen's Guide to the Darkness Below is a maze-like dungeon with an epic FINAL BOSS encounter. This adventure will work great as a one-shot, but also acts as the conclusion to the Dragon Town / Darkness Below campaign, picking up right where the Sky Garden (FSG 09) left off.
The primordial shadow has been locked in a magical prison deep underground for a millennium, but it's on the verge of escaping. A group of daring adventurers must delve into the Crystal Cavern and defeat the looming Darkness Below before it can escape to the surface.
This adventure is filled with whimsical illustrations, a maze-like cave map, lots of random encounters, some seriously weird NPCs, and a campaign-ending three part boss battle. Combat encounters include references to comparable 5E monster stats, otherwise, the zine has everything a DM needs to run this world saving finale!