I stumbled on this adventure when I was looking for something I can use as a Shattered Tower in Kelsey’s Gloaming and this sunken-fort-with-only-tower-above-the-ground is both perfect and original.
I made few changes (green knight instead of barbarian warlord for better fit in Gloaming; in throne room an hexling, shadowy demon who feeds on despair, bolstering Lady’s depression and causing subsequent literal depression of the fort; and Glimmer got more gnomish, subterranean appearance)
Definitely looking forward to playing it with my group!