Yeah, that's the one. He made a deal with an Original, baddest of all bad news back home, Klaus. I don't know where exactly he is right now, supposedly he's getting "better" since Lexi moved him into the house with her, but I know when I first got here he was in full-blown Ripper mode. In short? The emotional switch was turned completely to off, full-on vampire urges, no humanity left...
I don't want that because Ripper-Stefan isn't easily controlled, but Lexi is working to make him mostly nothing more than a human who happens to drinks blood, like her... Like it's a choice. I know my particular brand of nourishment doesn't exactly paint the prettiest picture...but it's what I have to have survive, Rikki. They'll tell you animal blood would suffice, but it doesn't, it's not the same.
....I get ranty about Stefan-related things beause I l, might be best to not go there, actually...