The Vampire Diaries is bringing on a couple more new characters for season 4. Looks like Klaus will be paid a visit by an ex-girlfriend. Spoilers below:
She is said to be in her early 20's and slightly un-kept. She's described as wild-eyed, beautiful and provocative and has carried a torch for Klaus for a number of years. In her case love, devotion and possessiveness can drive you go a little mad. Klaus will be shocked and worried at the measures she has taken to wait for him.
A new witch will be brought into Damon's fold when he goes in search of an older witch acquaintance for help.
She is the great-grand daughter of the older witch Damon seeks. She owns a small witch shop in the middle of nowhere. Damon is coming to her for help with a special spell that involves a lot of human blood. Things don't go well and Damon leaves very frustrated.