Don't let your players look at the wiki, I repeat, if any player looks at the wiki you have the right to legally attack him

By far the best 5e hardcover adventure, Curse of Strahd does a lot of things right: it has a compelling theme and atmosphere, an interesting setting full of complex NPCs, and a dangerous, iconic villain who will play to win. Strahd is not your ordinary final boss waiting in his castle for adventurers to come destroy him. He constantly meddles in the party's lives, playing an active role throughout the campaign. Compare him to Acererak in Tomb of Annihilation. Players in ToA might go through the whole module without ever discovering who Acererak is! He's just some lich guy who pops in at the end to kill them (if he's played well) or die (if he isn't). Even when he isn't taking center stage, Strahd is always lurking in the background. Just about every problem in Barovia can be traced back to him, which gives him a sense of omnipresence. Strahd feels like a true phantom in this adventure, haunting the party's every step. That atmosphere of dread is an essential part of gothic horror, and DMs will do well to put the fear of Strahd into their players early on.

Let's talk about why, five years after its release, CoS is still by far the most popular 5e adventure. All the strengths I listed stand out even more compared to other 5e hardcovers. The gothic horror genre gives the module a compelling and unique identity that's both attractive in itself (everyone loves vampires) and attractive in its difference. It's a tonal shift from standard D&D heroic fantasy. No other adventure besides Tomb of Annihilation (with its pulpy Lost World theme) rivals CoS in terms of atmosphere. CoS is gothic horror done well, hitting on themes of isolation, tragedy, and dread. Players are not heroes in a CoS campaign. Their goal is not to save the day (Baroiva cannot be saved) but to survive and, hopefully, escape with those they've grown to care for over the adventure's course. When DMs modify the campaign to make it less deadly or change it to allow Strahd to be permanently killed, they misunderstand what horror is about. It isn't about winning; it's about surviving. Victories in horror are intentionally small compared to victories in D&D (which is a genre in itself). Saving the kingdom from a vampire tyrant is a D&D victory. Saving yourself and the people that you love is a victory appropriate for gothic horror.

That being said, I can't really blame these DMs, because what they're doing is most likely what their players want. The reality is that, despite how hugely popular it is, most players aren't interested in playing CoS. Most players don't want the Gothic Horror Experience; they want the D&D Experience. As both a player and DM, I prefer it when moments of true victory are few and far between. In a setting full of darkness and pervasive hopelessness, moments of levity and hope feel truly special. Victory, in my opinion, savors sweeter when failure is more common than success. But I'm aware that my opinion isn't shared by the majority. Most players enjoy the power fantasy. They want their PCs to be capable and strong, they want death to be rare (and temporary, if it happens), and they want victory to be all but guaranteed (with minor setbacks being the worst outcome). Those are perfectly legitimate desires, but they are completely incompatible with gothic horror.

So what happens to most CoS campaigns, given this disparity between what the adventure offers and what most players want? Most CoS campaigns end up as Standard D&D dressed in a Halloween costume, with powerful heroes hacking their way through Hammer Film monsters. And, in my opinion, while that can be fun, CoS is all the lesser for it. I can't help but cringe when I hear stories about players mocking Strahd to his face (and getting away with it) or stuffing him into a bag of holding. I guess some people like those kind of shenanigans, but CoS isn't really meant for them. The mechanics of 5e are partly to blame, since they encourage the power fantasy mindset. D&D characters are meant to be strong; they're meant to be heroes. The end result is that even DMs who embrace the genre often find themselves playing tug of war with the mechanics.

Curse of Strahd is a great module trapped in a system that isn't a great fit for it and run by people who (frequently) aren't right for it. That being said, even when run as a bog standard D&D campaign, I think the adventure still outdoes its peers on the strength of its setting and characters alone. The campaign invites players to role-play in a richer and more nuanced way than D&D adventures typically encourage. For that, it deserves praise.

9/10

I'd also like to address DGoldDragon's review:

This is the most common criticism of Death House, that it's unconnected to the plot of CoS. While true, I'd argue that what it does is even more important: it sets the gothic horror tone. There's a great video on Youtube about all the ways that Death House foreshadows CoS. Strahd's story, at its heart, is a family tragedy, culminating in the murder of Sergei. Death House, too, is a family tragedy. It's also (as befits the name) notoriously deadly. Players can and will die if they aren't cautious (and even being cautious doesn't guarantee of survival). The final encounter with the shambling mound is meant to teach players to run away. If they stand and fight, they're going to die. This is an important lesson, because Barovia isn't scaled to the party's level. Some encounters are going to be too much for them (Bonegrinder and the coffin shop in particular come to mind), and they need to know when to run away from these. Those same encounters are the ones DMs tend to scale back, which, again, defeats the purpose of the horror genre.

I really don't understand how this adventure can be called "too easy" unless the DM is playing softball. Bonegrinder, the coffin shop, Yester Hill, and Baba Lysaga are all encounters that will wreck an average party. Strahd himself is almost impossible to beat if played optimally (as he should be with his 20 Intelligence). A DM who makes effective use of his lair actions will wipe the floor with a 9th level party. Whenever he gets hurt, Strahd can simply phase through a wall or sink through the floor to regenerate his wounds in peace. He can win through pure attrition if need be. It all entirely depends on how the DM plays him. If he just stands there and tanks the hits, he's going to die in 1-2 rounds.

I'm also not a fan of the Dark Gifts. I think they're poorly done. The Amber Temple as a whole is my least favorite part of the campaign. It's symptomatic of 5e's general lack of nuance. In older editions, the Dark Powers were mysterious, unfathomable entities who subtly rewarded evildoers, while karmically punishing them at the same time. 5e turns them into evil salespeople, hawking their Dark Gifts from amber stalls ("come get your Dark Gift of Tenebrous for the low price of $9.99!"). Blech. I just ditch the temple entirely.

I agree that revivify is a poor fit for CoS, but luckily the campaign doesn't hand out any diamonds. Seriously, there are zero diamonds to be found in the whole module. If players want resurrections, they need to either go to the Abbot or use the single scroll van Richten carries.

Firstly, if you are running this, skip the Death House and start your players at 3rd. It's almost entirely unconnected to everything else and it feels too much like filler. I have a feeling the designers knew this, and that this is why they put it in an appendix rather than in the Barovia chapter or a chapter of its own.

Bluntly, I think the adventure is too easy, with isolated exceptions. In particular, our 9th-level party (the recommended level for Castle Ravenloft) had no problem whatsoever dealing with Strahd, making it feel less like a struggle for life and freedom and more like a simple execution. We had left behind our prophesied ally, and the three items influenced things very little (the sunlight aura being the only bit even used during the fight), so it felt like the only pertinent thing we'd done in the earlier quests was gain experience.

The only adventure locations outside the Castle that I found compelling or interesting were Argynvostholt and the Amber Temple. And as far as the latter goes, I thought the Dark Gifts could have been done better. Roughly speaking, each had a side effect which was either a physical deformity or a personality flaw. The latter are quite interesting (assuming you actually roleplay them), but the former don't really do much, apart from possibly making NPCs react poorly (but by the time they have visited the Temple, they don't really need any NPCs to give a toss about them). I would amend most of the side effects to make them more subtle-yet-potent.

As a final note, the revivify spell is anathema to any sense of dread. Don't give them access to diamonds, or say the spell doesn't work at all within Barovia, or at the very least give revived characters madness, rather than just those resurrected after >24 hours. (I personally think that the creation of that spell was an exceptionally poor decision in the design of 5e, but that's beside the point here).

The is a powerful and challenging adventure, for players and DMs. Not for the faint of heart but greatly rewarding if you are prepared to take on the the extra work. Like many adventures, it requires polish (some area a LOT of polish) but it is and amazing and evocative starting point.

Et in Barovia Ego!

Love it!