Theme: Good - the environments are sufficiently metal. Unfortunately time constraints make spending some time on the namesake of the module a bit awkward. It's not fun for PCs to repeat the same saves 10 times in a row, so it's a challenge for the DM to make hellrocks falling on the party be exciting that many times.

Narrative: Average - The selling point of this module is that it's part of a series. It's definitely setting up a cool storyline, but it seems like the authors of the three modules (15/16/17) did not communicate with each other. Story details in the three modules do not match up.

There are also many many things which could have done with more explaining. The existence of the dungeon in the module does not make much sense, or at least, it needs more explaining by the module as I spent quite a bit of time puzzling it out so I could justify it to the players. Why did the devils only decide to attack the dungeon now? Did the Bloody Hooves freeze time inside or did Zariel? If it's the former why are they so powerful and if it's the latter how can there still be Demons inside? Why does it say that Dara needs to rest for 2 weeks if she has to go into the next two modules immediately?

No information on the arc's BBEG is provided in this module or the next two modules, it only says that he is loyal to Zariel (who is no longer an Archduke during the time of this module, so that just invites more questions), it does not state the type of devil they are, what powers he has, or his motivations.

Combat: Terrible - The module sends approximately 10 extremely weak combats at the PCs. That's not exciting, and it's definitely not doable in 4-6 hours unless the DM is handwaving combats away. There is a "mandatory" encounter table filled with under CR'd AND boring combats like "one madcap per PC, more if the party is too strong". The story significant encounters are also too weak, with the failstate of the final encounter being nearly impossible to trigger. Safe to say if you DM this you should be adjusting EVERY SINGLE COMBAT in the module significantly as the DM has no idea of the capabilities of a T3 party nor any idea of how long a single combat takes.

Editing: Terrible - Dara is supposed to be kept alive in this module, which has her statblock, but not the story award that you're supposed to give the players if she dies. Ironically the next adventure has the story award but not her statblock. The author also forgets the Levels of Madness mechanic comes from Rage of Demons storyline, not the DMG, so the mechanics of this special madness effect is not printed in the module. In general the module is also plagued with the S8/S9 module writing guidelines which are terrible for DM readability, and the author did not mitigate this at all.

Overall, this module's main selling point is that it's the setup to the first part of the trilogy- the next two modules do not provide a good recap. The skeleton of the plot is also usable, but you will need to provide the meat of every encounter yourself. The time pacing of this module is abysmal- if this is meant to be an atmospheric module, why are there so many combats taking up all of the time budget? If this is supposed to be a hellish combat-focused module, why are the encounters so weak?