Nightstone Keep (5E)

From publisher blurb:

Nightstone Keep by Ed Greenwood (for 4 to 6 characters from 4th and 6th level)

This location-based adventure is centered on a ruined, long-disused stone keep in a temperate wild forest area (possibly not far off a caravan road or forest trail). The characters will be able to explore the ruins of the keep, which have become a plant colony, and attempt to wrest a powerful treasure from the clutches of the araunglyd, a gigantic sentient fungus. The araunglyd will attempt to thwart the players at every turn, using its drone-like minions to harass and hinder them as they go.