Eidolon

The term derives from Ancient Greek εἴδωλον (eidolon), etymologically related to eidos ('form, appearance'), and in classical poetry it names an image or appearance of a person rather than the person in full. In epic and tragedic uses (attested in Homeric summaries and later poets such as treatments of Helen by Homer and Euripides, and reports of Stesichorus' poetic strategies) the eidolon is a literary device that allows poets to separate visible image from ontological being — for example, to argue that Helen’s physical body was absent from Troy while an image (eidolon) was what others perceived. Modern uses in comics, games, and manga adopt the lexical form for varied supernatural or game mechanics but are creative adaptations rather than continuations of classical ritual belief.

Classical sources describe eidola as look-alike images or phantom doubles of human form — shade-like apparitions or phantoms that resemble the living or the dead. Specific passages summarized in the sources depict them as shade/phantom appearances (for example, Homeric accounts and the Odyssey summary in which Theoclymenus sees the doorway 'filled with them'). The classical material treats sensory details (clothing, translucence, coloration) flexibly as determined by poetic context; the recurring markers are likeness to a person and a non-corporeal, image-like mode of presence.

In the classical literary tradition eidola function chiefly as apparitions or image-presences: (a) they appear as images of the dead (shade-like appearances) and (b) they can stand in for a person 'in propria persona' in narrative terms, allowing the poem to present someone as present while the physical body is elsewhere. Homeric uses show eidola perceived by the living (affecting perception and narrative events) — for instance, massed apparitions after violent deaths in palace scenes. Classical sources do not ascribe to eidola consistent independent agency or world-altering powers; their role is primarily a literary/poetic mechanism. Modern fictional sources repurpose the term for varied supernatural mechanics (e.g., demonic attachments, memory-absorbing shapeshifters, spectral fragments), but these are adaptations rather than classical attestations.