How would you use this riddle in your campaign?

So I’m gonna be running a one shot on Halloween for my D&D group and I’m trying to think of questions to ask myself to help with writing it (and any other one shot in the future)

The questions I have so far are:

1. What story do I want to tell?
2. What is the theme? (Whodunnit, Romance, Heist etc)
3. What is the setting? (High Fantasy, Sci-Fi, Noir etc)
4. Am I using pre generated characters?
5. What level are the characters?
6. What are the encounters?
7. How do I expect the story to end?

Are there any other questions that you can think of that would be helpful in writing a one shot?

Also the intention is for this to be useful for anyone who is wanting to write a one shot, so feel free to steal the idea!

Edit to add: Dyslexia strikes again with the title of the post 🤦🏻‍♂️