Every colt and filly knows that, when Nightmare Night rolls around, it's time to dress up in one's favorite costume and go out trick or treating. It's a tradition as old as Nightmare Night itself, and probably the best there is for collecting treats, but what ever happened to the tricks?
This year, Princess Twilight Sparkle may just find out, for although Equestria prospers, the passion between her and her wife, Rarity, has begun to cool. Rarity has ideas, but whether or not Twilight will like them, or indeed, she herself, is uncertain. Of course, it's not much of a trick or treat if you already know what's coming.
Will Twilight experience her deepest, darkest fantasies, or is there something sinister at play, waiting for the right moment to make its move.
Trick, or Treat?

Story will contain: hypnosis, (illusory) dubious consent, domination, pseudo-incest, various F-F and M-F sex acts, and some truly depraved cuddling and fluffy pillow talk. Read at your own risk.

Written as an entry for the Incest is Wincest group's October Spoopy/Costume contest.

Editing assisted by best animal dolphin42