Orpheus is a mystical world that was ruled by vampiric trancers called Nobles. Their leader was Caliban. Prior to the reign of the Nobles, Orpheus was ruled by a wizard. The wizard was murdered (poisoned) by Caliban.
The surviving humans formed a resistance group called the "Tunnel Rats" and Jack Deth aligned himself with them against the Nobles. One of the very few other known human survivors who saved Jack, then turned out to be in alliance with the Nobles.
Orpheus is home to Caliban's Castle and the Castle of Unrelenting Terror, from which no one has ever left upon entry. No one that is except Jack Deth, Prospero and Caliban, who stalked them to the castle disguised as a dog (or wolf).
Inside the castle was the Tiamond, a large jewel Jack required to get back home. In order to obtain the Tiamond, Jack and Prospero had to overcome many dangers.