Using PROPER PARAGRAPH form, you can either write:
From the perspective of a child going through a very scary haunted house for the first time, including everything they would hear, feel, barely see, etc.
You can describe the scariest costume you can imagine. Include clear descriptions of colours, looks, everything. This can be a costume that you've worn, want to wear or just thought of.
The goal for this is for you to practice your descriptive writing and using different, powerful adjectives that will help you TERRIFY your reader. Transport them to the haunted house, or create the costume in the mind so they quake with fear. Good Luck! MWAH-AH-AH!