In Dumblebore's office, Harry sat with Gandalf. Suddenly, a shadowy grey dementor appeared behind Harry. Harry turned to Gandalf, explaining the appearance of the boggart. "Boggarts appear in the form of whatever the person fears most. Dementors feed of happy feelings, til nothing is left but your most unbearable and awful memories." Harry shivered after stating this. As if sensing Harry's sadness, the dementor loomed closer behind Harry, growing larger with each step. Harry slowly turned around, preoccupied with his memories of the triwizard cup, and took out his wand. "Expecto pat-" Harry's eyes then rolled up in his head, and he fell to the floor. Sensing his hesitation, the boggart grew even larger, and stepping forward, suddenly disappeared with a large pop. Harry groaned and rolled over. "What happened?" Gandalf answered, "I believe that the boggart simply ran out of unhappy emotions. Because of your explanation, I had no fear, and the boggart had used up too much energy growing. At the absence of a source of energy, is ceased to exist. Hmm, that was indeed one of my more profound ideas." Stroking his long white beard, he smiled. Harry chuckled. "Gandalf, you are so much like Dumbledore."