If you want to know if someone is "real" tell them an obvious lie. A human will recognize it for what it is immediately, a cursed will not. They may look real, but they are not. Only real eyes realize real lies.
This could be used to show how archetypes change through time in literature. The sirens in The Odyssey are quite different from the siren as a mermaid, or even the more modern sirens in Harry Potter.<<< Or idk man they could just be SWS lyrics