The setting is a planet that has several regions, mostly medieval in technology level. Each region's people has a strange power; the story begins in the region of a people with enhanced healing. However, sometimes the healing factor goes too fast and starts growing too many/incorrect body parts; these misshapen monstrosities with dozens of limbs etc are kept in pens and I think harvested somehow? I forget the details.
The prince has recently begun to grow breasts, an obvious precursor to this condition, which will inevitably progress. He escapes (with the help of someone, I think?) and leaves the country before he is penned as well. He travels to many places, at some point is captured by lawmen, executed via crossbow, and buried, all of which he survives by virtue of his hyperactive healing. He eventually reaches a forest where the tribal inhabitants can accelerate and decelerate the flow of time around them, and learns to do this. The chieftain is relatively young upon meeting the main character, but is older by the time he learns the tribe's power. It is revealed that the cheerful and energetic chieftain has been living at an accelerated pace for quite some time and will soon die of old age. When this happens, main character and his girlfriend from the tribe decide they have nothing in particular to stick around for, and have time-dilated sex in public incredibly slowly for several real-time generations. He leaves, I think leaving her behind, and goes to a desert? Where he meets a hermit who teaches him genetic manipulation and fixes the error in his healing factor that causes it to generate extraneous body parts, while leaving it operating at its accelerated (even for his people) rate. Also something about sand, maybe telekinesis?
I don't remember much else about the book and the events may easily be out of order. I think the book itself was a relatively small hardback, with a cover either tan or off-white.
