Masks are worn for a number of reasons. They can be worn for protection, disguise, entertainment, or for a performance. Many different cultures have incorporated masks from carnival to totems. Masks can add an element of intrigue and romance.

Image from pikist
The Prompt:
Write about a world were the main character wears a mask. Describe the mask and why the main character wears it. They could be a champion of justice, a criminal, or whatever you decide.