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.

Rowling doesn’t disclose a name, but she notes that “the woman in question returned my antipathy with interest. Why we took against each other so instantly, heartily and (on my side, at least) irrationally, I honestly cannot say.”

(Imagine trying to sleep knowing that the richest writer in the world hates you – and has 400 million fans ready to do her bidding. … Whoever you are, when you’re ready to come forward, please know that The Washington Post is eager for an exclusive interview.)

Among other revelations, we learned Friday that Umbridge is not only wicked, she’s a hypocrite. Despite her claims, she’s actually half-Muggle!

Rowling also offers new thoughts on the dreaded Azkaban prison, the Ministers of Magic and Thestrals (a kind of magical horse with bat wings).

A publicist said Rowling posts new content on Pottermore about every two months.

—From news service reports