I've been worried that this one is a bit too hard, so as a clue, this feature could take a hundred years after a momentous event to show itself.
With what are Men too easily satisfied?
This being too easily satisfied with whatever-it-is might, in the future, have led to children in Gondor playing unsavoury games of let's-pretend. No doubt if they did, some old people might be writing letters about it ...
as extracted from....the inevitable boredom of Men with the good; there would be secret societies practising dark cults, and 'orc-cults' among adolescents...
The Letters of J.R.R. Tolkien, #338 From a Letter to Fr. Douglas Carter 6[?] June 1972....a tale supposed to refer to the end of the reign of Eldaron about 100 years after the death of Aragorn.
Since we are dealing with Men it is inevitable that we should be dealing with the most regrettable feature of their nature: their quick satiety with good.
What bore Sauron's device but were not his servants?
The brief glow fell upon a huge sitting figure, still and solemn as the great stone kings of Argonath. The years had gnawed it, and violent hands had maimed it. Its head was gone, and in its place was set in mockery a round rough-hewn stone, rudely painted by savage hands in the likeness of a grinning face with one large red eye in the midst of its forehead.
Flies, dun or grey, or black, marked like orcs with a red eye-shaped blotch, buzzed and stung