Changeling
Roger Zelazny
 The people had long suffered under Det Morson's power. When at last, the wizard Mor joined the fight, Det and his infamous Rondoval castle were destroyed. But the victory was not complete, for the conquerors found a baby amidst the rubble: Det's son, Pol. Unwilling to kill the child, Mor took him to a parallel world where technology ruled and the ways of magic were considered mere legends. He substituted Pol for a baby of the same age, using a spell to persuade the parents to recognize him as their own. In order to retain the balance between the worlds, Mor took the baby from the other world and brought it back to his own, leaving it with a local artisan, Marak.