The Dark Circus, or Circus of Stars is run by a man known by inhuman kind to hate humanity. Not many particularly care, as they tend to stay out of the Circus's way. The Circus itself takes in the most broken down of creatures, who make deals with the Ringleader to work for him until he decides to let them go (or they disappear, more often than not).
It has become a hidden practice within the circus to seek out the less desirable of humanity and have them dealt with as they come in. How this happens depends on how the ticket seller, Naava, marks them, as well as who finds them after.

Arethusa has joined the circus by the guiding hand of Eros, to find her lost thread. With any luck she can bring some peace to the circus members as well as restore her own power.