From back cover Berkley paperback September 1984:

It was a new word for Hell. An escape-proof prison mine, where the worst criminals in the Universe were condemned to perpetual suffering in the ruby darkness.

Aton had committed the unpardonable crime. He was condemned to Chthon for loving the minionette, the sensuous siren-spirit no man was allowed to possess... or even desire.

And to find out who she was and why she was forbidden, Aton had to do what none before him had ever done. Escape from Chthon!