Soul Splitting

The Key of Oz has the power to separate someone into two people. The soul of the victim is broken in two, with one "good" side and one "bad" side. The good side is kind and caring while the evil side is sadistic and cruel. They are connected and feel the same pain, if one were to die the other would as well and when the curse is broken the two halves become one again.

History
In There's No Place Like Home, Sam and Dean find that Charlie has returned from Oz and is going after the person who killed her parents in a drunk driving accident, something that was covered up. Charlie proves to be violent and goes as far as torturing people and slashing the Impala's tire to keep the Winchesters from following her. However, it turns out there are two Charlie's: Good Charlie and Dark Charlie. Good Charlie explains that in Oz, she and Dorothy fought a war to free the land from evil and were losing so Charlie made a deal with The Wizard of Oz in which the Wizard used the Inner Key of Oz to split Charlie into her two halves and Dark Charlie single-handedly won the war, though she did a lot of bad things in the process. Afterwards, Dorothy and the Wizard became the new leaders of Oz and Good Charlie followed her dark self to Earth to stop her from doing more bad things and to lock her up forever. Sam and Dean convince Good Charlie to reunite with her dark half who can't be killed without killing Good Charlie so Sam and Good Charlie travel to the Bunker to research the Key to Oz in hopes of repairing it as Dark Charlie broke it. Their research leads them to former Man of Letters Clive Dylan who had discovered the Key and been trapped in Oz. Clive is unable to help them repair the Key, but he reveals himself to be the good side of the Wizard who is evil and power hungry, the two having been split by a coven of witches in Oz. In order to stop the Wizard and Dark Charlie, Clive shoots himself to force the Wizard to come to Earth to heal Clive and himself. At the same time, Dark Charlie visits Russell Wellington, the man who killed her parents and convinces Dean to let her talk to Russell. Dark Charlie claims to forgive Russell, then kills him and flees. After visiting Dean in a bar, she steals the Impala and follows Dean to Clive's house where the two fight and Dean breaks her arm and brutally beats her. The Wizard of Oz arrives and chokes Sam while Good Charlie feels the pain of every hit Dean lays on Dark Charlie. In order to stop the Wizard and at Clive's insistence, Good Charlie reluctantly shoots Clive, killing him and the Wizard. Sam stops Dean from beating Dark Charlie to death and he is able to use the Inner Key of Oz, taken from the Wizard's body to reunite the two Charlie's. Two days later, Charlie, unable to return to Oz, decides to help Sam and Dean find a way to remove the Mark of Cain and forgives Dean's actions even though he refuses to forgive himself.

Known Examples

 * Charlie Bradbury
 * Clive Dylan