A rager is a person with a special ability for fighting. They are natural borne killers and fight with a skill that takes most people years to learn. However when they fight they pay attention to nothing else and they have difficulty stopping at first and must learn to control their gift. There are only two ragers in the books as they are extremely rare. They are Ripped and Gregor. According to twichchip, a sent seer (a gnawer with the special ability to see what they smell) ragers excret a certain scent when they fight.