The story centres around Dolores Umbridge, who has never quite been on Potter's good side, reported E! Online.
"Umbridge is not only one of the most malicious Potter characters, she is the only person other than Lord Voldemort to leave a permanent physical scar on Harry," the website wrote.
Rowling, 49, explained why she chose to write about the character, saying, "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. What sticks in my mind is her pronounced taste for twee accessories."
She said Umbridge is one of the characters in the Potter story, she dislikes the most.
"Dolores, who is one of the characters for whom I feel purest dislike, became an amalgam of traits taken... a variety of sources. Her desire to control, to punish and to inflict pain, all in the name of law and order, are, I think, every bit as reprehensible as Lord Voldemort's unvarnished espousal of evil," the author said.