Who is Erasmus Fry, from "Calliope" from The Sandman and what is their importance?

Erasmus Fry studies mystical arts. At the young age of 27, Fry knows the proper rituals to capture and bind a muse, Calliope. Fry uses Calliope to become a famous and wealthy author, keeping her captive and raping her. Fry seems to have no conscience. He trades Calliope for a bezoar to protect him from poison, even though he has promised Calliope that he would free her. The story implies that Fry also has the Sandman held captive and that at Fry's mysterious death from poison, the Sandman escapes.