The Magnum Opus — the Great Work of alchemy — occupies a pivotal position in depth-psychological literature as both a technical term from Hermetic tradition and a master metaphor for psychic transformation. Jung established the foundational interpretive move, reading the alchemical opus as a projection of unconscious individuation processes: the Work’s dual aims, rescue of the human soul and salvation of the cosmos, map directly onto the psychological drama of integrating shadow, anima, and Self. Edinger elaborates this reading systematically, tracing the sequential operations — nigredo, albedo, and beyond — as stages of psychological mortification and renewal. Hillman complicates the teleological framing, insisting that the telos of the opus must remain interior to the work itself, functioning as purposiveness rather than an externalized goal, and affirming that the nigredo is precisely where the magnum opus properly begins. Giegerich introduces the sharpest critical tension, distinguishing rigorously between the opus magnum and the opus parvum: the Great Work operates not on personal consciousness but on the collective, culturally objective life of the soul, enacted ‘in Mercurio’ rather than in private individuation. This distinction reframes Jung’s own oeuvre — his published psychology, not his personal dreams — as the genuine magnum opus. Together these voices triangulate a core debate: whether the Great Work is properly a personal, therapeutic, or civilizational achievement.