What character might be appropriate to audition for Macbeth, other than the characters in the play?

Audition requirement is a Shakespearean monologue not in the the Scottish play. I'm looking for a character that can very well portray characteristics of the witches and Lady Mac. I've thought of Ophelia. Her suddenly unhinged mind like Lady Mac, with the kind of enchanted spirit like a witch, but perhaps Ophelia isn't severe enough to be like these characters. She seems more playful in her tragic cirstance. Maybe a fairy from Mid Summer? Of course that would plainly be for a witch. Any thoughts?