«Thongor Against the Gods» by Lin Carter

A new ruler has arisen on the ancient continent of Lemuria. It is Thongor the Barbarian, whose dauntless courage and mighty sword have made him overlord of a thriving young empire. Against him conspire in secret those dedicated to the Black Gods of Chaos. Suddenly Thongor's wife, the Princess Sumia, is abducted. Thongor speeds to her rescue — but his enemies are cunning as well as ruthless. Embroiled deeper and deeper in a danger compounded of both sorcery and science, Thongor learns that he must carry his battle to the Gods themselves!