Neptune occupies a distinctive and contested position within the depth-psychology corpus, functioning simultaneously as an archetypal principle, a symbolic map of the collective unconscious, and a clinical diagnostic instrument. The major voices — Greene, Sasportas, Tarnas, Cunningham, and Rudhyar — converge on Neptune as the planetary emblem of dissolution, transcendence, and the boundaryless stratum of psychic life, yet diverge sharply on its therapeutic valence. Greene reads Neptune as a fundamentally feminine, self-sacrificial archetype aligned with collective emotional drives and the suffering mediatrix, potentially hostile to individual psychological integration. Sasportas approaches Neptune house by house, mapping how its suppression generates unconscious enactment and how its conscious embrace can open the ego toward genuine spiritual wholeness. Tarnas situates Neptune within grand historical cycles — especially the Uranus-Neptune and Neptune-Pluto conjunctions — arguing that its archetypal field shapes entire epochs of cultural vision, from religious awakening to the emergence of the unconscious as a conceptual category. Cunningham foregrounds Neptune’s pathological pole: addiction, psychic permeability, and the self-destructive pursuit of artificial transcendence. Dennett synthesizes these threads through a clinical case study of Bill Wilson, treating Neptune and Pluto as the primary archetypal complexes governing addiction and recovery. Across all positions, the central tension is between Neptune as liberator — dissolving ego into compassion, mystical union, and wholeness — and Neptune as destroyer of psychological boundaries, enabling illusion, addiction, and identity diffusion.