The Borgias' David Alpay has joined the cast of The Vampire Diaries in a recurring role, TVGuide.com has learned.   Alpay will portray Professor Shane, an attractive and charismatic believer in the occult who has a history with Bonnie Bennett (Katerina Graham) and her family.   Secret Circle alum to come between Vampire Diaries' Tyler and Caroline   The Canadian actor, whose other credits include The Tudors and Fairly Legal, will first appear in the fourth episode of the upcoming season. He joins the previously cast Todd Williams, who will play a vampire hunter, Phoebe Tonkin, who may come between Tyler (Michael Trevino) and Caroline (Candice Accola), and Grace Phipps, who may be a possible new ally for Elena (Nina Dobrev).