The uroboros — the serpent devouring its own tail — stands among the most architectonically central symbols in the depth-psychological corpus. Erich Neumann provides its definitive psychoanalytic theorization in The Origins and History of Consciousness, where it designates the primordial, undifferentiated state of the psyche prior to the emergence of ego-consciousness: hermaphroditic, self-begetting, self-devouring, the pleroma from which all subsequent psychic differentiation proceeds. For Neumann, the symbol is not merely cosmological but ontogenetic and developmental: the uroboric stage of the infant psyche — narcissistic, autarchic, enclosed — is the necessary precondition for all later self-formation and individuation. Jung engages the figure chiefly through its alchemical and cosmological avatars, linking it to Aion, eternity, and the Mercurius duplex, where it functions as an image of the prima materia and the coincidentia oppositorum. Edinger integrates the term into clinical discourse, treating uroboric containment as a measurable stage on the ego–Self axis. Critical voices, notably Hillman and those he influenced, have challenged Neumann’s developmental schema as too committed to a progressive, Apollonic heroism — a tension that runs beneath much post-Jungian clinical theory. The uroboros thus sits at the intersection of developmental psychology, alchemical symbolism, and the phenomenology of the unconscious, remaining an indispensable heuristic across the tradition.