Since I will no longer be running these, I can give away the secrets.
It was a lost Netherese "storybook" that would reset when people left. The Heroes (tm) were the "children" brought in. The witch that suggested they find the Heroes (tm)? Was the storyteller.
The story evolved based on what characters believed and thought. So if the character firmly believed in fae, it would behave as if fae rules were true. If you believed in demons, they were real. If you believed singing would make little birds swarm to you like Cinderella, so it was. Just like it would work for children believing in Santa Claus - he's only real if you believe he is!
As a librarian, I hope you'll all continue to be inspired to look up the true fairy tales each of the adventures was based on. If you want suggestions, just reach out and I can recommend some fun (non-standard) tales!
RJ