Hold the Mushrooms Please

From the introduction:

Arriving at the small village “Binbibo”, [the characters] see worried villagers. Three children may have fallen in a sinkhole, last seen by a ranger. The sinkhole is deep and strange mushrooms are growing from it. As one of the fathers descended, he was mysteriously freed from his rope, but yells back he’s alright: colored lights lining the walls feathered him down into the strange alien cavern. There doesn’t appear to be an immediate way up.