With A Tangles Skein by Piers Anthony (Book 3)

When the man Niobe loved was shot, she learned that she had been the target, in a devious plot of the Devil's. Hoping for revenge. Niobe accepted a position as one of the three Aspects of Fate, only to find that Satan's plots were tangled into the very Tapestry of Fate. Now the Evil One was laying a trap to ruin Niobe's granddaughter Luna, who threatened his plans—and he had tricked her son into Hell.Niobe's only chance to save her son and Luna was to accept a challenge by the Prince of Deceit—a challenge to be decided in Hell and in a maze of Satan's devising!