This Dark Sun adventure follows on from Black Flames and Merchant House of Amketch only in the sense that the required level for the PCs has increased. To make these three (or four if one includes Black Spine) a proper series, there really needed to be more plot arcs. This was achieved (albeit not at a high quality level) with the original Freedom - Road to Urik - Arcane Shadows series.
As per the title, the adventure is set in and around Nibenay. The set up starts with the assumption that the PCs are there somehow. This could fit in naturally with any number of plot hooks or trading adventures. Regardless, they will be approached by either the Veiled Alliance, or the Templars of Nibenay to aid them in a raid / ambush for them. Although there is a refreshing appearance of choice, the path through the adventure is the same either way, whichever faction the PCs wind up working for (and even more refreshingly: they can choose neither and still be on track for the adventure).
Suddenly: something happens! The raid gets derailed by the Sorcerer-King attempting to wipe out the Zwuun - an entity described in Veiled Alliance who is opposed to the King. Lightning arcs across the palace and the surrounds. Then there are earthquakes, acid rain and in general: end of the world style apocalypse on the city-state of Nibenay as a result. Runaway magic turns the dead (stored in underground crypts in Nibenay) in to zombies and creates nasty flora that also want to kill the citizens and PCs. The Veiled Alliance and the Templars put aside their differences and try to figure out what is happening. And the faction associated with the PCs takes them to the King's palace to try to locate the Shadow King himself and figure out what is happening.
Although there are plenty of details about the palace, the PCs can largely bypass this and head straight for the inner citadel. Therein, they find the King engaged in a silent psionic battle with the Zwuun, whilst Siemhouk (an NPC noted in several books) looks on. The PCs basically have to protect Seimhook whilst she attempts to calm the Zwuun and various nasties including elementals attack all around. Should they win, Nibenay might re-think his approach to the city and become more engaged. Or it might go back to factional warfare. But the former is probably more interesting given that something similar happens after the Prism Pentad has taken place.
The strong points of this adventure for me are the open ended nature of the introduction, coupled with the apocalyptic state that the city-state winds up in and how the PCs attempt to solve the crisis -- very epic. The negatives are that it should be more grand and sweeping. An introduction to the Zwuun, some familiarity with Seimhouk, etc., should come before all of this adventure ideally so that it can build up more slowly. Its not brilliant, no where near the epic coverage of Merchant House of Amketch for instance, but it is good. So 3 out of 5 stars from me. Possibly 4 on a good day with a bit more preparation and build up. Worth running, unlike some of the other adventures.