I picked up Van Richten's Guide to Ravenloft and have been reading it cover to cover. This is my review of the book, chapter by chapter. Chapter 3 covers over 30 domains, so I'm posting about it as I work my way through the different domains.
The next domain in the book is Carnival, a fascinating deviation from the formula (such as there is). The carnival is a moving domain of dread. It moves because it is, as its name suggests, a literal carnival.
I admit I was skeptical at first. How could a traveling carnival also be a domain? In-game, I'm as fine with that concept as I am with magic and faeries and all the other fantastical ideas in D&D, but as a Dungeon Master how would it work? It just didn't seem like there would be enough material for it to be a whole domain that player characters couldn't escape. Not because it's implausible, but just because I didn't feel there'd be enough story material.
Then I remembered a horror movie I saw that was set not just in a carnival, but inside a haunted house inside a carnival. And a Tunnels & Trolls solo game that takes place entirely in a bizarro circus tent. In fact, when I run games at conventions, my rule of thumb is three dungeon rooms equal 2 to 3 hours of playtime.
Of course there's enough material for a carnival to be an entire domain.
Then it struck me that if you have this book, there's no way you're going use all 30 domains before 5e is ancient history (or the Earth's ecosystem implodes, whichever happens first.) Problem solved! Trap the player characters in a traveling circus that moves from domain to domain by design. Show them every single domain of dread over the course of 30 weeks.
Of course, this book isn't exactly built to support that, at least not the way Saltmarsh or even Yawning Portal are. By that I mean, this book doesn't have adventures written out for you to run. But it does have plenty of story ideas for each domain, and most domains have plenty of material on what makes the unique, so you have plenty to work with.
I love the idea of a traveling domain, and I love a good carnival setting. The Lightwick Market, a group of straggler fae who follow the carnival around, is a great (and arguably under-developed) idea too. I don't know whether these fae are bound to the carnival or whether fae can just move through Ravenloft freely, but I'm intrigued by Ravenloft being part of the Shadow Plane now, and I think this lore of the Carnival brings a lot of cohesion to the setting.
There are too many clever ideas in the Carnival for me to spoil, so I won't comment any more on this domain, aside from saying that it was a pleasant surprise for how unique it is, and it kind of makes me want to go buy The Wild Beyond the Witchlight now.