The nightmare demon occupies a richly contested space in the depth-psychology corpus, functioning simultaneously as a medical phenomenon, a mythological figure, and an autonomous psychic force that resists reduction to either category. The primary theoretical tension runs between the Freudian-Jonesian hypothesis — that the nightmare demon is a product of repressed erotic wish, distorted by psychic censorship into demonic form — and the mythological-archetypal position advanced by Roscher and elaborated by Hillman, wherein the demon is not a symptom of faulty psychodynamics but an autonomous numinous power that instigates both desire and dread. Roscher’s scholarship, the foundational text in this corpus, traces the nightmare demon across Greek (Ephialtes, Epiales), Roman (incubus, pilosi, Faunus), and pan-European folklore traditions, consistently identifying Pan as the paradigmatic figure: goat-formed, shaggy, erotic, nocturnal, and essentially linked to suffocation, sleep paralysis, and collective panic. Hillman radicalizes this by insisting that the nightmare demon must be encountered on imaginal rather than naturalistic terms — the demon is not explained by respiratory mechanics or repression but is itself an archetypal reality. Jung contributes the figure of Lilith as nightmare-lamia, while Woodman and Ogden address the demonic nocturnal encounter from clinical vantage points. The stakes are epistemological: to reduce the nightmare demon to pathology is to miss what it means that the ancient world named it a god.