Epigraphs are like little appetizers to the great entrée of a story. They illuminate important aspects of the story, and they get us headed in the right direction.
"Did I request thee, Maker, from my clay
To mould me Man, did I solicit thee
From darkness to promote me?"
—Paradise Lost, X, 743-45
Have you ever screamed at your parents, "I didn't ask to be born, anyway!"? Well, that's pretty much how the monster feels about being created by Frankenstein. Also, the clay business gets back to the Prometheus title. Ah, beautiful.