Professor Slutborn is the Portents Professor at Hogwarts in the 1980's. Ebony describes him as a "tall gottik man wif long blak hair, pail skin and blue eyes wering a suit and blak Cronvrese shoes." He also looks like Charlyn Manson. Ebony steals an Amnesia potion from his "efface" in Chapter 37. She plans to use it on Tom Satan Bombodil to make him fall in love with her faster. He walks into the office, asks what she's doing here, and then it appears that she asks him the same question back - as if he needs a reason to be in his own office. However, Ebony immediately afterwards claims she 'thought it was class', which he believes and lets her go. Slutborn inexplicably appears in the final chapter, though it is not set in the 80's. He delivers the final pun, of "Oh my goth!".
It appears that Professor Slutborn is very loosely based on Professor Slughorn from the books. His existence in the story may suggest Tara had a vague idea who he was even though the film of The Half Blood Prince was not released until 2009. She may have actually read the books (considering she knew of Dolores Umbridge, whose first film appearance was not until 2007, and Tara mentions Order of the Phoenix coming out soon in one AN), or more likely gotten Raven to tell her about them. Either way, Slutborn bears next to no resemblance to his canon counterpart at least in terms of appearance.