I'd give this episode a 4/5, but I'm extremely disappointed by the plot.

The majority of the episode is great. Baba Yaga has always been one of my personal favourites when it comes to folklore. The Doctor teamimg up with Vasilisa also provides great dynamics. And it's an absolute delight to hear the Doctor being confused by Baba Yaga's magic (which is something I think future writers should explore on, the Doctor is always so dismissive and knowitall when it comes to "magic", I know this is a sci-fi franchise but it'd be fun if the Doctor gets stumped by all the magic stuff every now and than). Mention of Koschei the Deathless was also an interesting little cherry on the top(KOSCHEI MENTION, THOSCHEI FOLKS WE WIN THIS), if only Baba Yaga cared to say more about this alleged husband of hers. It'd be great to have the Doctor saying that classic mouthful of a sentence(A needle inside an egg inside a duck inside a hare inside a box buried in the forest of the island Buyan)

And then it all goes crashing downhill.

"Oh, you're a creature from local folklore. So you must be a product of superstition and psychic manifestation and positive feedback loop."

Words can't even begin to describe my disappointment when it turns out that this episode fell victim to this classic and now abused trope. I hate it when they use great story materials like this. It's lazy and irresponsible. This episode would have been so much better if Baba Yaga really was a powerful entity (from the Dark Ages or somewhere eldritch, whatever, I don't really care as long as a real entity). But no, they had to make it predictable and mediocre. This really drains all the fun and life out of this episode.

So, yeah. I can't say I hate this episode, I really rather enjoyed it. But I'd be lying if I say I'm not incredibly disappointed by how the whole thing turned out.

Fun episode. Would make a great memetic SCP story.