Mood Candy is a type of Elvin treat that changes flavor based off the taster's mood. During Sophie's first midterms, Keefe gave these to Sophie and all his other friends, with a note on Sophie's saying:
“For the Mysterious Miss F—If you don't relax, this candy will always taste bitter--so snap out of it! And try to stay out of detention!”
—Keefe Sencen, in Book 1: Keeper of the Lost Cities
While the candy had originally tasted like sugarplums, as soon as Sophie noticed the necklace in her locker it turned bitter because she changed moods. Keefe continued to give his friends mood candy the next year, with an exception of Sophie, to whom he gave paintings. Livvy said she always has this candy in supply, and that during Sophie's forgotten memory of what happened with her limbium allergy, she had given Amy one.