The Locket (トレビン torebin) is a tool of Oliver's used to store pieces of heart (こころのカケラ fragments of heart). Oliver receives the locket from Old Father Oak in the very beginning of the game and continuously wears it around his neck.
Heart pieces are otherwise known as "emotions" or "virtues", and if there is a lack of one in a person, they become "brokenhearted". In this case, "brokenhearted" doesn't refer to sadness but refers to someone emotionally stunted in some way, ranging from acting rude to acting like a blank slate. If their missing emotion isn't restored soon, they may become afflicted with nightmares. While an excess of a particular emotion can be just as bad as a lack of it, it's unclear if it should still be called "brokenheartedness" in such cases.
Characters may have an emotional imbalance at any given time, and while excess of emotion can be sensed by the locket's radar, a lack of emotion can't be. Typically the lack of an emotion/virtue is due to Shadar influence, whereas an excess can be due to anything, for instance a happy occasion. Oliver can take a piece of heart from a character by casting Take Heart. He can give away a stored piece of heart by casting Give Heart.
In the NDS version, while the locket can apparently store more than one copy of the same emotion at once, the in-game screen only shows the player as actually owning one copy. In the PS3 version, the player can really only store one piece at a time, and furthermore can only take an emotion from a character once during the game, even if later on they have another excess.
In the PS3 version, which pieces of heart are needed and in which order they appear have something to do with the main storyline. In the NDS version, they possibly appear in a different order. When an emotion goes missing the character exhibits the opposite of the missing emotion in all cases except for "love", where the opposite isn't hate but "indifference".
The emotions/virtues are:
- While not being heartbroken, fairies occasionally and similarly need pieces of art in order to mend their comedy routines if they've gone wonky.