The vagus — from the Latin for ‘wanderer’ — occupies a foundational position in the depth-psychology literature shaped by Stephen Porges’s Polyvagal Theory, and its clinical elaborations by Deb Dana, Jan Winhall, and others. Within this corpus the vagus is not treated as a single nerve but as a hierarchically organized ‘family of neural pathways’ whose evolutionary stratification mirrors the phylogenetic history of vertebrate survival. The corpus is organized around a tripartite schema: the ancient, unmyelinated dorsal vagal circuit (immobilization, collapse, dissociation), the intermediate sympathetic chain (mobilization, fight-or-flight), and the uniquely mammalian, myelinated ventral vagal circuit (social engagement, co-regulation, safety). The central tension in the literature runs between older autonomic models that privileged sympathetic arousal as the index of emotion and Porges’s insistence that the vagal system — particularly its parasympathetic, cardiac-regulatory functions — is the primary substrate of emotional life. A subsidiary debate concerns the validity of respiratory sinus arrhythmia as an index of vagal tone. Therapeutically, the vagus is reconceptualized as a resource: the ‘vagal brake,’ ventral vagal tone, and the face-heart connection become levers for clinical intervention in trauma, addiction, and developmental dysregulation. The compassion nerve, the smart vagus, the wanderer — these epithets accumulate across the corpus to characterize an anatomical structure that has become a master metaphor for psychological regulation.