Dreaming Caverns of the Duergar

From the cover:

While journeying through the treacherous peaks of the Ul Dominor mountains, the heroes are caught in an avalanche! They find the road ahead blocked by rubble -- as well as the road behind. But the avalanche opens a cave in the mountainside, leading to a labyrinth of dark, forbidding caverns. With nowhere else to go, the heroes make their way into the unexplored cave, and soon find themselves battling duergar cultists with a sinister agenda...