As promised, this Halloween morning J.K. Rowling has posted new free entries on Pottermore, her Web site that offers related features and retail products to Harry Potter fans. One item of particular interest to all young wizards is an essay about Hogwarts Professor Dolores Umbridge, whom we met in “Harry Potter and the Order of the Phoenix.” Rowling reveals for the first time that this maniacal character is based on an actual person.