Rowling has said that Dumbledore is primarily self-taught, although he "had access to superb teachers at Hogwarts," and, as far as his education is concerned, "Dumbledore's family would be a profitable line of inquiry." While he is not vain, Dumbledore also exhibits no false modesty, readily acknowledging that he is unusually intelligent and an exceptionally powerful wizard. He admits a number of times to Harry in their occasional meetings in Half-Blood Prince that he makes mistakes, and since he is smarter than most men, his mistakes "tend to be correspondingly huger." Dumbledore is an expert at nonverbal spells and is famous as an alchemist who has worked with Nicolas Flamel, the only known maker of the Philosopher's Stone, and is credited with discovering the twelve uses of dragon's blood. His Patronus takes the form of a phoenix, a recurring symbol in the books. His knowledge of the most powerful kind of magic, love, is extensive. He taught Harry about its very essence, and the innate power of his ability to love his parents, which eventually helped Harry realise his destiny to kill Lord Voldemort. He is known to be able to conjure Gubraithian fire (magical everlasting fire). He has claimed to be able to become invisible without using an invisibility cloak, which is a powerful Disillusionment Charm. Dumbledore is also skilled in Occlumency and Legilimency. Dumbledore is an expert at Transfiguration too, having taught the subject before becoming headmaster. He frequently creates complex objects like sofa chairs out of thin air (or from less comfortable chairs). Dumbledore is also proficient at Charms and Potions; according to the obituary written by Elphias Doge, his papers were published in journals such as Achievements in Charming and The Practical Potioneer. Dumbledore is famous for defeating Grindelwald, who is second on a list of Most Dangerous Dark Wizards of All Time only to Voldemort himself, in a "spectacular duel of legend", succeeding in doing so despite the fact that Grindelwald possessed the Elder Wand, which supposedly guarantees invincibility in duels due to its power. His skill at duelling is further shown when he calmly engages Voldemort in Harry Potter and the Order of the Phoenix, overpowering him and eventually forcing him to possess Harry to be spared from total defeat. (It is known in retrospect that Dumbledore possessed the Elder Wand when duelling Voldemort, having taken it from Grindelwald.) Unlike most wizards who make