(I know people will not like it, but here we go again with the cringe)

This is aswell a conflicting equestrian memory from Incognito, this time from luna, no, nightmare moon, did you ever thought about what was nightmare moon's nightmare? Now you have a answer, luna can't be sure if this was a memory or a nightmare indeed, it sometimes pop in her head as a wierd dream of her, which in theory was not suposse to happens, since she is the one controling the dreams, but this creature that she don't know it is a human, gave her a nightmare when she was nightmare moon that she could not control, a mystery that come to her mind time to time but then put it aside, because she thinks is not relevant, only intriguingly to her, since she don't remember what happened next and don't like to think about nightmare moon's acts so often.

Just wait until twilight sparkle finds out about that nightmare from her, it would cost many hours of research for purple smart... and luna's time.