Charon: A Dragon at the Gate (The Four Lords of the Diamond, Vol. 3)

They took the body of Park Lacoch and stripped away his mind. Then they stuck him aboard a spaceship and exiled him to Charon, from which no return was possible. And just when he thought things couldn't get any worse, Park found himself transformed into a changeling -- a half-beast, half-man, with the beast rapidly gaining ascendancy . . .