In this paper I show with the help of an illustrative case how: (1) the mystical experience may represent a culmination of a transitional mode of relatedness; (2) the mystical experience itself may then become a transitional phenomenon; (3) multiple previous experiences with controlled illusion and hallucinogens may facilitate this experience; (4) the quintessence of the mystical experience specifically—and the transitional experience generally—is an upsurgence of residual primary narcissism; (5) such an upsurgence can be in the service of defending against overwhelming loneliness; therefore, the mystical experience can become a special, potentially adaptive, ego mechanism of defense.