The ancient word of the day is Uncanny. This is the feeling of encountering a landscape, person or object that is both frightening and unsettlingly dissonant. Freud coined a similar word for this “unheimlich”— which is to say, eerie and both homely and unhomely. I’m sure you would be able to recall some uncanny encounters, where things just weren’t quite what they seemed!
Robert Fergusson and the Uncanny
For this some ca’d him an uncanny wight, The clash gaed round, “he had the second sight.” – Poetical Works of Robert Fergusson (published 1773; OED’s 1st citation of uncanny as “associated with supernatural arts or powers.”)
Heimlich: The things that creatures do secretly when no one is watching.
What uncanny experiences have you had in your life, that you can’t forget about?