Hiero's Journey (Bantam Science Fiction)

Per Hiero Desteen was a priest, a telepath—and a highly trained killer. Together with his great riding moose and the young bear who was his friend, he was on an extraordinary mission. For this was five thousand years after the holocaust known as The Death. Now the evil Brotherhood of the Unclean was waging all-out war against the few remnants of normal humanity, determined to wipe out all traces of its emerging civilization. Hiero's task was to bring back a lost secret of the ancients that might save the humans. But his path lay through the very heart of the territory ruled by the Unclean and their hordes of mutated, intelligent, savage beast followers. And the Unclean were waiting for him!