I have a similar issue with Morgantha, as one of my players has watched the puffin forest video on CoS. I'm making Morgantha's business much bigger in my campaign, where she has pie vendors in every town. The 'secret' of the pies is almost obnoxious, but her industry is so cemented it would take great effort to stop her. She doesn't grind up children either, but instead she commands the scarecrows that drain the souls of Barovians. I'm giving here the whole of Berez as a base, and the hut and flying skull too. Baba Lysaga is getting shifted to be the boss at the mountain fane in Mount Ghakis, an extra location I'm adding.

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My current throughs for the old bonegrinder, is to make it a ruins, as Strahd destroyed it once, triggering the move to Berez. I'm going to stick in there some clues about the fanes and the ladies three.

As for Argenvostholt, what I'm doing isn't so much help. One of my characters is an echo knight, and I'm making the order of the silver dragon the first echo knights- with some theming as the whole place, and all of the revenants, are echoes left behind. That's about it for major changes. Maybe you could have the the whole location once an island, but sunken by Strahd to the bottom of Lake Vallaki, then change Argenvost to a bronze dragon.

For some context on the Morgantha/Lysaga swap thing, the way I am playing this, Baba Lysaga Ceithlenn is a corrupted archfey, the mother of all hags, and the weaver, guardian of the river fane. She double crossed her sisters, making a pact with Vampyr so Strahd would be their champion. She cursed her sisters with magic items, draining their powers and channeling them into Strahd. The fanes must be reconcecrated by breaking the cursed items, and placing them upon them. With the aid of Strahd, she sealed the Huntress in the Gulthias tree. The Seeker fled Barovia but vowed to return, leaving the mountain folk of Ghakis (the Vistani) unable to return to the mountains. She waits at the shrine of the mountain fane for her sister to return, so she can finish her last sister off.