Monsters populate horror, fairy tales, fantasy, and legends. Their purpose is to frighten. To provide a focus for our collective and personal fear.
Because fear takes many forms, monsters take many forms. They are supernatural or otherworldly and often ugly. They want something and they act on that desire with little thought for consequences to anyone else or even themselves. They are beastly, driven by instinct. It makes them cruel.
My favorite stories are about befriending monsters. Stories of taming dragons, of falling in love with the ogre, or of accepting the demon within.
For this theme I chose creatures of the dark. Characters who wrestle with their compulsion toward evil. Characters who are powerful and frightening and intoxicating.