This is not a regular adventure - this is an epic. Its an entire campaign rolled in to one release. Its extent is grand: featuring treks across the entire known world and unexplored regions therein. It is the strongest departure from the story arc in the books that accompanied the release of the Dark Sun setting, and whilst technically the climax of the Freedom, Road to Urik, Arcane Shadows and Asticlian Gambit story arc, it most certainly can be played as a stand-alone adventure.
The major premise of the adventure is that The Order (who you've not heard of before, but if you had the prescience of running this adventure might have placed clues in the previous ones yourself) - the folks who are at the peak of psionic power on Athas - have decided that no one but them should wield psionic powers. Accordingly, they have created the psionatrix: a device that dampens psionic activity throughout the land making it tougher to use and limit the power levels of users in general.
Clearly, this does not go un-noticed. If they played Arcane Shadows, then Korgunard will contact them to investigate (why he can't do this himself being an uber spell caster and psionic master himself is dubious in extremis). They figure out that Hamanu, the Sorcerer-King ofUrik, could be behind it. But he isn't. And he says go to an old fortress and have a look there. So off to the Silt Sea and the Road of Fire to explore. Cutting a long story short, the PCs will eventually figure out what is going on (as well as being stalked by members of The Order, who are actually split by factional lines) and head to the Dragon's Crown mountains to attempt to destroy the psionatrix (which is where it is located).
On the plus side, the scope of this adventure is magnificent - no less than 7 playable "parts" which will require plenty of sessions to resolve fully. The possibility for role-play is very high (including driving Thri-Kreen crazy due to the psionatrix field) as well as interaction with characters from previous adventures. Thankfully Korgunard doesn't feature too heavily in the latter parts (immmm - he perishes! oops - spoilers!). And the whole "you're captured and turned in to slaves" meme is largely missing … except for encounters with Hamanu…
As with the other adventures within this arc, planning is essential to a full enjoyment of the adventure. Having little hooks in previous adventures and cues to characters within this one would be great. Also, the GM should feel free to ignore some of the more "you must end up here" kind of nudges - having the scope of an adventure this large is excellent and many tangents are possible and should be followed. But the GM must be prepared to go down these sidelines and not get narrow vision to plough through the plot no matter what.
Overall, this is very close to 5 stars, but given the railroading at various points and the turned-in-to-slaves meme repetition, I can only give it 4. Large scale action, high stakes outcomes, important NPCs doing things, and a GM ready and willing to give it a good whirl adds up to an excellent conclusion to the story arc begun in Freedom.