THE POWER OF THE BELT AND CORONET

When Flor the serf, a common beater in khada hunts, kills an Earl with his club, he steals that earl's two talismans -- a belt and a coronet that bestow great mental powers upon their user. Flor the serf learns to use these powers. He kills a free swordsman, takes his clothes and flees his native land to become Florel Derikuna, a Baron with designs upon a neighboring noble's daughter.

Medieval Fantasy?

No. Science fiction.

For the belt and coronet are items of high technology in a low civilization.

And Konar and Meinora of the Philosophical Corps, an interplanetary secret service, must sort this mess out