Slumbering Tsar: The Hidden Citadel, Part 3: The Throne of the Demon Prince

From the publisher's website: Ever upward the heroes climb through the great Throne of Orcus discovering the Artisans’ Quarters, providing clues to the true fate of the citadel’s inhabitants, the malefic Serpent’s Coil, the Creeper of the Halls, and the heritor’s of the Hidden Citadel’s guardianship from long ago.