Confessors have an additional power called the Con Dar, also known as the "Blood Rage." The Con Dar is the Subtractive counterpart to the Additive Magic of the Confessor's touch. Confessors' usual powers come from love and compassion. Correspondingly, the Con Dar originates in vengeance and hate.
Only the strongest Confessors possessed this ability. The ancient magic of Con Dar was rarely used and it was previously thought that it could only be taught to a Confessor by her mother once she reached the proper age. However, Kahlan Amnell was able to enter the Con Dar by instinct alone upon learning of the supposed death of Richard Rahl, despite having never been taught due to her mother's early death. Once released, there is nothing the Confessor can do to suppress the Con Dar.
The power of the Con Dar cannot be used for a Confessor's personal gain. It can only be invoked on behalf of a loved one of the Confessor's. Once a Confessor has entered the Con Dar for the first time, they can only subsequently enter it in defense of the person for whom it was initially entered.
The Con Dar's primary function makes the absolute protection or vengeance of this person the ultimate goal of the Confessor. The Confessor becomes irrevocably fixated on it. She therefore usually ends up taking radical or irrational measures that kill her before the Con Dar finishes its course.
The Con Dar also equips the Confessor with further magical powers that aid her on her quest of protection or vengeance. The need for physical contact to administer the Confessor's touch is eliminated, as is the recovery period needed to recharge the power. In the television series Legend of the Seeker, the Confessor can also confess multiple people at once, as well as having increased strength and endurance. Kahlan Amnell, if not all Confessors, can also conjure blue lightning while in the Con Dar, whose Subtractive Magic allows it to defeat underworld creatures like the screelings.
In Legend of the Seeker, it appears that the indirect Confession of the Con Dar that requires no contact can be deflected by wizards.
It also appears that in Legend of the Seeker, the Con Dar is not trigger-locked to whomever the Confessor first enters it in defense of. In the Episode "Broken", Kahlan enters the Con Dar upon learning that Cara had murdered her sister. In the Season 2 finale "Tears", Kahlan again enters the Con Dar in defense of someone other than Richard (whom she entered the Con Dar for the first time in the Season 1 episode "Conversion"); Nicci, who has used Kahlan's own Confession powers against her.
It is traditional for a Confessor in the Con Dar to use a special ink to paint two bolts of red lightning across her cheekbones. The effect is quite frightening, a warning to the innocent to stay out of her way.