A rager is a berserker, a natural-born killer capable of an adrenaline-induced trance in which the body's natural abilities of strength, speed, and agility are greatly enhanced, known as "raging." "Raging" allows the rager to perform feats of incredible power and agility, usually in relation to fighting, which can allow them to take on hundreds or thousands of enemies successfully. Ragers will experience this as their vision "splintering," until all they can see is the victim's most vulnerable points, which they will then strike at with unerring accuracy. Most also experience a loss of memory (ie not remembering killing their attackers, only 'waking up' once they are dead and the raging ends). Even without any martial training, ragers are natural fighters, and are considered 'one man/one woman armies.'
The downside of these gifts is that while in full rager mode, a rager is usually incapable of controlling himself or herself, and has no thought towards his/her own self-preservation or anything else besides the target, leading them to crippling injuries or mutilation because they didn't defend themselves, or leading to their friends getting killed in the backwash. Even when not all out raging, a rager is usually hard-pressed to control their violent urges, and is thus prone to violence and killing, causing most ragers to be rejected from society as a whole.