I actually asked this question a while ago! I'm on mobile so I can't link you, but the construction topic for the ride here has a good explanation of the storyline behind the ride.
Essentially, a sorcerer named Volkov has put a curse on the town of Novgorod, and you have to free it. In the end Volkov is burned and that prop that falls from the ceiling is his burned body. There's way more to it but that's all I know off the top of my head.
I was actually kicking myself for not putting this in my "Quirky Bucket List" thread the other day, it's definitely one of the top things I wanna ride in Europe.