Within the depth-psychology corpus, ‘Mystery’ operates on at least three distinct but interpenetrating registers: the cultic-initiatory, the psychological-transformative, and the ontological-religious. The cultic register is most thoroughly documented by Burkert, Kerenyi, and Jung/Kerenyi, who treat the ancient Greek mystery traditions—Eleusis above all—as paradigmatic instances of structured encounter with the ineffable, wherein secrecy, initiation, and the hierophant’s revelation constitute a formal grammar of psychic transformation. At the psychological register, Moore, Woodman, Eliade, and Hillman attend to mystery as the irreducible opacity of the soul itself: that which resists cure, demands care, and deepens through rather than despite its obscurity. The ontological register emerges in Campbell’s comparative mythology and in Louth’s treatment of Orthodox sacramental theology, where mystery names the fundamental condition of being’s excess over any conceptual grasp. Tension runs throughout: Trungpa pointedly challenges the depth-psychological inflation of mystery as a category, arguing that labeling the unknown merely perpetuates metaphysical confusion. Harrison and Seaford complicate the picture further by tracing mystery’s genealogy through social ritual and pre-Socratic philosophy. Jonas and Gnostic sources introduce mystery as revealed gnosis—hidden knowledge disclosed to the elect. Taken together, the corpus positions Mystery as neither mere obscurity nor mere secrecy, but as a structuring principle of the psyche’s encounter with what exceeds it.