The Cyborg and the Sorcerers by Lawrence Watt-Evans
Del Rey, 1982
Price I paid:
Slant the Cyborg Warrior had been ordered to kill the enemies of Earth and return with their weapons technology. His robot spacecraft was to see that he did―and kill him if he didn’t.
Problem was―Earth had perished three hundred years before, and no one had told the ship.
Slant’s dilemma seemingly had no solution…then they landed on a strange world where the computer detected “gravitational anomalies.”