Phthor

The return to the caverns of Chthon! The planet Chthon was a prison world of ruby caverns where rebels and outlaws were exiled to endless darkness. Aton's crime was loving a minionette, one of the sensuous woman warriors it was death to touch. His son Arlo was both minion and human. Arlo's destiny was war with the deadliest enemy of all - the very planet Chthon, which was alive and furious at the life forms within its depths.
Piers Anthony is the acclaimed author of more than 100 novels and short story collections. His works include the Xanth series, the Mode series, Chthon and Total Recall.