“The Vampire Diaries” is returning for one last run. Friday’s midseason premiere kicks off the final stretch of episodes before the series finale, and it looks like there might be a role reversal. When the show went on hiatus, the Salvatore brothers made a deal to save Caroline and Alaric’s twins. Stefan turned off his humanity and went off with Damon to gather souls for Cade. In Season 8, episode 8, we’ll see just how evil Stefan can be.