Perhaps I missed something, but I've gone over this one a few times and I just cannot understand how you are supposed to run the puzzle encounter towards the end. As others have said, predrawn maps will help tremendously (I ran mine on a virtual tabletop with the images directly pulled from the PDF) but other than the puzzle encounter, this one goes pretty quickly.

The first encounter is laughably easy, but it is kind of supposed to be so that's no problem. The second encounter was infuriating for my players because of the creature's tactics and abilities, but it's ability to actually harm them was almost nil. Mostly it was just chasing this thing around and failing to hit it while being subjected to sleeps and charms and other enchantments.

The final encounter could have theoretically been interesting, but with a Master Summoner on the table, it was over in the blink of an eye. Overall, I would not recommend this one.

This scenario offers excellent RP opportunities, rewards well-rounded characters played by smart and resourceful players and offers a really serious challenge.
Also, GM must be well prepared and predrawn maps significantly speed things up.

I played through this scenario with level 1 characters. There's an encounter in the scenario which appears to be borderline impossible (if not, borderline impossible) to beat after you learn the full circumstances of the encounter via metagaming. You can't design a tier 1-2 with that kind of encounter in the game.

Aside from that, it seemed like a pretty straightforward scenario, which only added to the deadly surprise later on.

I didn't have a closer look at higher tiers, but at higher levels, characters probably would have been better suited to handle it.

If you're one of those GMs that like to run the scenario "as is", this is not the scenario for you. Unmodified, this is a 2 star killer scenario that should be avoided. Even victorious, your players will likely be annoyed and won't have fun.

As others have already stated, this is a killer scenario (especially with the optional encounter). Ideally you should have 6 PCs and the group should be APL 3 at subtier 1-2 and APL of 6 at subtier 4-5 (to avoid a TPK).

Having said that, with some modifications, this scenario is great. One of the best aspects of this scenario is that it oozes dark gothic horror, that was fun to GM. Even the intro was fun.

Length: Long. I thought it was going to take 5 hours and it took almost 6 hours. To fit into 5 hours, much handwaving has to be done (and the optional encounter skipped).
Sweet Spot: Both subtiers are equally good.
Experience: GM subtier 1-2.
Entertainment: Overall DV is fun, although the optional and final encounter can be frustrating.(9/10)
Roleplay: This scenario has some fun roleplay at the start and some interesting interactions later (depends on GM). (10/10)
Combat/Challenges: Too deadly at times. The puzzle the PCs are meant to solve is unlikely to be solved without modifications. (4/10)
Uniqueness: It's memorable, hopefully not for the wrong reasons. (9/10)
Faction Missions: Average Mcguffin and they don't really add anything the scenario. Then again, you probably wouldn't have time for anything more involved. (7/10)
Overall: With changes to the final encounter and puzzle, this is a great and memorable scenario. Unmodified it's a mess and frustrating at best. (9/10)

I highly recommend reading the GM thread on this scenario and I'll post my thoughts there.

The GM should modify the puzzle in the scenario. As written, most groups won't even get the clues needed to solve the puzzle. Even with the clues, my group of players almost didn't figure it out (it took 20+ minutes).

Edit: Bumping to 5 stars since this is exactly the kind of scenario I like, with the exception of the problems with the final encounter and puzzle.

The reason I bought this scenario was because of the creepy dark horror theme, and I wasn't disappointed. So if your players like dark horror themes and you're willing to heavily modify the main puzzle and the final encounters, your players will have a good time.

I played this recently, and I have to agree with the other reviewers who were irritated by some of the combats. Having a combat under difficult conditions does not necessarily make it interesting; on the contrary, it often makes it a frustrating, tedious slog when several PCs can only make minimal contributions.

Similarly, I find challenges that require the use of a particular skill (which can't be used untrained) to be irritating as well, especially since I usually play in "pick-up" groups where we rarely have a balanced mix of classes.

On the positive side, I liked the initial story behind the mission, although the actual module was a very linear dungeon crawl.

I just played this module recently at a convention, and can honestly say that my experience playing this game was annoying beyond words. Not wanting to get into too many spoilers, there are some combats in this game that, if the players are not completely prepared for with the right mix of spells, skills, or special abilities, the combat can be incredibly deadly or take annoyingly too long.

Fortunately, for my table, we were of sufficient level and experience that the combat was not threatening our characters' survival, but it got so annoying at one point that one of the players literally threw up his hands and walked away from the table for 20 minutes before he came back saying he was ready to continue.

The only suggestion that I can give without crossing the "spoiler line" is that DM's and players need to READ THE TITLE OF THIS MODULE and take it to heart.

Beyond the two combat scenes that annoyed the players beyond words, the rest of the module was incredibly well written and provided some great RP encounters. Tim Hitchcock and Mark Moreland usually do amazing work with their modules, and this module is not a complete bust. However, I will say that it's not the best work they've ever done.

I recently ran this. I absolutely loved the first encounter. I ran it with newer players, I like tough encounters, but I think it could be hard/deadly for most allot of groups, which isn't a bad thing.

I think it could be a bit tough on 1st level characters.

After running and playing in this module I found that it was inappropriately deadly, particularly for first level characters.

One encounter was literally and thematically opaque to the degree that players could not reasonably find the solution to the problem, and PCs were being one-shotted.

In both games I participated in the only reason the players were able to survive was due to very large table size, giving enough targets for one or two players to be able to eventually have the time to solve the issue. If these had been a standard four person party they would have resulted in TPKs.

That just isn't right, especially for a low level module.

The other big problem, which seems common with most of the PFS modules, is that what is actually going on with the elaborate backstory is not in any way adequately conveyed to the players. They stumble from one encounter to the next, getting attacked by seemingly random things, and not really getting a clear idea of what is going on.

If this was a home game and had relaxed time requirements, it would be possible for a GM to orchestrate things so that the larger context could be drawn out, but in a living campaign environment, where you are trying to cram a whole session into four hours, all of this is lost.

Modules need to be tighter, more direct, and have appropriate challenges for the levels that you are playing at.

I played this adventure just today and it's on my "never again" list along with the horror that was Skeleton Moon (for interestingly the same reason). It doesn't get one star like Skeleton Moon did, simply because I loved the creative use of the main foil, but it only barely does so. There was only a very small amount of potential roleplay, at the very beginning, and the module quickly degenerated from there into one tough combat after another. The "device" was an interesting addition, and I liked thematically the climax, but again, it was all set amongst the guise of "too difficult."

Honestly I don't get the appeal of the module and found it horribly overrated. It was easily the slowest module I've played through so far, and for something set in Ulstav, I expected it to be A LOT more creepy, but when you find out right away it's a Darklands module, that excitement waned (talk about a bait and switch). I didn't like how the adventure doesn't play well without certain classes, and woe to the group that doesn't have a cleric for no reason other than it has the potential for horrible player deaths (at least at Tier 1-2 where we played). From Tim Hitchcock I expected so much more, which only added to that disappointment.

I will note: I don't mind a challenge, but the potential lethality of this module was inappropriate. I don't care what level you're playing at, creatures with base damage capable of insta-killing party members are neither fun, nor a "challenge" they're just outright cruel to players and do nothing but discourage the player it happens to. This is especially true in Pathfinder Society where a lot of times you're trying to encourage new players to join. 1st level PCs should not be meeting up with one, let alone three creatures that can one-shot party members via spells, special-abilities, or bonuses due to the encounter nor should they have to deal with a certain optional encounter that is all but impossible for a low-level party. In fact, I counted no less than four of these kinds of issues with this module.

I really like this scenario but it is difficult to run well. Give away too much and the climax is a cakewalk. Give away too little and it’s a bloodbath. As much as I complain about cakewalk encounters, I don’t enjoy it when the players feel as if they’re trapped in a no-win situation. I’ve only killed one PC in the 4 times I’ve run it so far. I guess that’s not awful. Deadliness aside, Tim and Mark did a masterful job delivering an engaging scenario. There’s some fun role-play in the beginning, followed by a mystery, some creepy discoveries and then a lot of player apprehension. I love seeing classic/obscure monsters used in so appropriate a setting. The scenario contains great campaign setting flavor. Practice a Slavic accent for the NPCs, and if that fails just go with your best “Borat”. Some of the faction missions are alright, none of them really stand out though. That’s a missed opportunity. The maps are all excellent though. A fun, frightening adventure.