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.
Tepest is listed as "folk horror", and so this section focuses on the "quaint" beliefs of the people of the domain, and how they give power to subjugation, abuse, and brutality. The domain's darklord is Mother Lorinda, a green hag who's captured her sisters in a cauldron so she can use their magic for her own goals. Her main goal is to have a daughter, and she uses as much black magic as necessary to try to create one out of twigs and brambles and animal parts for herself. She ends up making monstrosities, of course, but to fuel this and the rest of her power, she demands a ritual sacrifice every quarter. The people of Tepest serenely oblige, in the way that only religious fanatics can.
I think the most disturbing thing about Tepest is the creeping knowledge that everyone in the village of Viktal (the domain's only remaining village) is one wrong word away from zealous rage. Everything's fine until you question their devotion to Mother. Nature and civilisation exist in complete harmony until blood must be spilled. There's nothing strange about Mother Lorinda until you see through the illusory magic. But no matter what, of course, you're the bad guy, not the people leading a town youth out into the middle of a field for ritual slaughter.
I think "folk horror" almost undersells a setting like this. This is psychological horror, with gaslighting and deception at every turn.
Although it has an intriguing backstory, Tepest is one of those domains that doesn't have a strongly suggested plot. As usual, there's an adventure hook table to help you come up with an excuse for the player characters to spend time there, but I have a feeling that eventually most player groups are going to gravitate toward the mysterious nature of the local religion. And if not, it wouldn't be hard for the locals to find something to become angry about. Anything that appears to go against Mother Lorinda will do, and it doesn't even have to make sense. Any player character might say the wrong thing, or look different than what the villagers are used to, or could be deemed "impure", or too old, or too young, or too happy, or too sad. Tepest is a tempest ready to trigger at any moment, or not at all. Either way, the horrorific reality of the Tithe festival, and Mother Lorinda's brutality, is going to become clear, and it's up to the player characters whether or not that's important to fight.
This is a good, creepy, unsettling domain. The next one is the last one (sort of)!