A Wizard in Midgard — Christopher Stasheff

Under the nom de guerre of Gar Pike, renegade psychic wizard Magnus D'Armand travels the stars fighting injustice and oppression like his father, Rod Gallowglass, the Warlock in Spite of Himself.

Now the Rogue Wizard wanders the galaxy alone, having lost his best friend and partner in liberation to the lure of love. He finds himself on the distant planet Siegfried, which is beleaguered by racism and prejudice--a tough nut to crack, even for an experienced psychic liberator. Can Gar teach the peoples of Siegfried to live with and love one another? And, most importantly, can he teach a lonely girl to live with and--dare he hope--love him?