From publisher blurb:
This adventure supplement is a special collaboration with another creator we feel fortunate to call a friend, The Fluffy Folio. In Eyes in the Dark, a group of level-3 adventurers travels to Haverton, a city beside the Firefly River. The recent earthquake in the area caused some landslides that revealed a cavern network where the river meets the mountains. The people of Haverton did not know of this place. However, in a similar way, a new world appeared for the indigenous monsters of these caverns.
Nothing good came out of this. Curious children got lost, and city guards lost their lives. Too many people have gone missing in the past four weeks. Haverton looks for external help and offers a hefty reward to anyone who can eliminate all threats in the cave. The adventurers may also be hired by Mikaelus Fluffus, a famous biologist who wishes to study the monsters within the cave.
This is a level-3 adventure that takes the heroes to a cavern network near the mountains. They must deal with the eye-stingers and brain sharks there. Ultimately, it is the adventurers' job to find a way to make these ecosystem work or remove all monsters from the area...