As for what Teknogamer said...
What if Chzo just wanted a perfect prince? The arrogant man was not within the beliefs of the Cult of Agony at all, as in, he didn't suffer the mind, body and soul until Chzo had him. Perhaps you're right in the ultimate punishment, but look at the new prince.
Body: Broken bones etc
Mind: Fear, boredom, confusion
Soul: Making him fall in love and ripping that away from him.
My problem with this approach was that a few questions are left unanswered.
First, in general you'd have to explain what the function of a prince is, until now I was assuming based on given information that the prince was there merely to bring chzo to this world, now that we see he doesn't want that what could chzo want a prince for? Especially considering that the bridge between worlds existed only for moments, so the prince won't be able to go to the world of technology and within the world of magic chzo is powerful enough (if not the most powerful) and wouldn't need a prince.
Secondly, this still doesn't address the issue of the false prophecies. The explanation I gave would explain this. (But if you answer the first question, explaining why chzo would need a new prince, then potentially you could answer this by explaining that chzo knew the druid wasn't the perfect prince and set up this whole system merely as a means of getting someone else)
Lastly, I'm not sure if the new prince is so much better than the old prince. The old prince was placed into a tree, where the body of the tree went through much suffering (as seen throughout the story) his soul is eventually destroyed, and as for his mind, this absolute betrayal and all the prophecies being false may be a mental torture (all the which are of greater severity than the new prince's woes). Also it seems funny that the new princes sufferings are so unique, I'm sure in the thousands of years there have been people who suffer more, physically/mentally/spiritually, and chzo could have arranged the bridge for a different time.
Thus based on the above I attempted to explain the new prince as being signifcant only in as much as he increases and emphasizes the old princes punishment and suffering.