If it's the one I'm remembering, it's a step more nasty than that. The regenerating character is the Chosen of one of the setting's gods, and has a fairly high position in the city guard. Two other guards have some beef with him, and manage to kidnap him and hand him over to the vivisectionist. They've also been trying to shut down the vivisectionist because they are not comfortable with him experimenting on slaves, but since it's legal there's nothing they can do about it. So they sort both issues by giving him a victim that doesn't need replacing, and get rid of an uncomfortable person. Win!